Population | Definition, Trends, & Facts

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id="content" class="md-content"> <div class="md-article-container template-desktop infinite-pagination"> <div class="infinite-scroll-container article last"> <article class="article-content container-lg qa-content px-0 pt-0 pb-40 py-lg-20 content md-expanded" data-topic-id="470303"> <div class="grid gx-0"> <div class="col-auto"> <div class="topic-left-rail md-article-drawer position-relative d-flex border-right-sm border-left-sm open"> <div class="drawer d-flex flex-column open"> <div class="left-rail-section-content"> <div class="topic-left-rail-header text-truncate bg-gray-50 position-relative text-right d-flex align-items-center"> <div class="tlr-title px-20 py-15 text-left"> <em class="material-icons text-gray-400 d-lg-none" data-icon="toc"></em> <a class="font-serif font-weight-bold text-black link-blue" href="https://www.britannica.com/science/population-biology-and-anthropology">population</a> </div> <button aria-label="Close" class="js-sections-close-button btn-link btn-sm btn d-lg-none position-absolute top-0 p-10 right-0" > <em class="material-icons font-26" data-icon="close"></em> </button> </div> <div class="section-content pl-10 pr-20 pl-sm-50 pr-sm-60 pl-lg-5 pr-lg-10 pt-10 pt-lg-0 bg-gray-50 clear-catfish-ad"> <div class="toc mb-20"> <div class="font-serif font-14 font-weight-bold mx-15 mb-15 mt-20"> Table of Contents </div> <ul class="list-unstyled my-0" data-level="h1"><li data-target="#ref1"><div class="pl-25"><a class="link-gray-900 w-100" href="/science/population-biology-and-anthropology">Introduction</a></div><div class="ml-40 toc-drawer sub-toc-drawer"></div></li><li data-target="#ref60653"><div class="d-flex align-items-center"><button class="h1-link-drawer-button btn btn-xs btn-circle d-flex rounded" type="button" aria-label="Toggle Heading"><em class="material-icons font-18" data-icon="keyboard_arrow_right"></em></button><a class="w-100 link-gray-900" href="/science/population-biology-and-anthropology#ref60653">The basic components of population change</a></div><div class="ml-40 toc-drawer sub-toc-drawer"><ul class="list-unstyled" data-level="h2"><li data-target="#ref60654"><a class="w-100 link-gray-900" href="/science/population-biology-and-anthropology#ref60654">Fertility</a><ul class="list-unstyled" data-level="h3"><li data-target="#ref60655"><a class="w-100 link-gray-900" href="/science/population-biology-and-anthropology/Biological-factors-affecting-human-fertility">Biological factors affecting human fertility</a></li></ul><ul class="list-unstyled" data-level="h3"><li data-target="#ref60656"><a class="w-100 link-gray-900" href="/science/population-biology-and-anthropology/Biological-factors-affecting-human-fertility#ref60656">Contraception</a></li></ul><ul class="list-unstyled" data-level="h3"><li data-target="#ref60657"><a class="w-100 link-gray-900" href="/science/population-biology-and-anthropology/Biological-factors-affecting-human-fertility#ref60657">Abortion</a></li></ul><ul class="list-unstyled" data-level="h3"><li data-target="#ref60658"><a class="w-100 link-gray-900" href="/science/population-biology-and-anthropology/Biological-factors-affecting-human-fertility#ref60658">Sterilization</a></li></ul></li></ul><ul class="list-unstyled" data-level="h2"><li data-target="#ref60659"><a class="w-100 link-gray-900" href="/science/population-biology-and-anthropology/Mortality">Mortality</a><ul class="list-unstyled" data-level="h3"><li data-target="#ref60660"><a class="w-100 link-gray-900" href="/science/population-biology-and-anthropology/Mortality#ref60660">The epidemiologic transition</a></li></ul><ul class="list-unstyled" data-level="h3"><li data-target="#ref60661"><a class="w-100 link-gray-900" href="/science/population-biology-and-anthropology/Mortality#ref60661">Infant mortality</a></li></ul><ul class="list-unstyled" data-level="h3"><li data-target="#ref60662"><a class="w-100 link-gray-900" href="/science/population-biology-and-anthropology/Mortality#ref60662">Infanticide</a></li></ul><ul class="list-unstyled" data-level="h3"><li data-target="#ref60663"><a class="w-100 link-gray-900" href="/science/population-biology-and-anthropology/Mortality#ref60663">Mortality among the elderly</a></li></ul></li></ul><ul class="list-unstyled" data-level="h2"><li data-target="#ref60664"><a class="w-100 link-gray-900" href="/science/population-biology-and-anthropology/Mortality#ref60664">Marriage</a></li></ul><ul class="list-unstyled" data-level="h2"><li data-target="#ref60665"><a class="w-100 link-gray-900" href="/science/population-biology-and-anthropology/Migration">Migration</a><ul class="list-unstyled" data-level="h3"><li data-target="#ref60666"><a class="w-100 link-gray-900" href="/science/population-biology-and-anthropology/Migration#ref60666">Early human migrations</a></li></ul><ul class="list-unstyled" data-level="h3"><li data-target="#ref60667"><a class="w-100 link-gray-900" href="/science/population-biology-and-anthropology/Migration#ref60667">Modern mass migrations</a></li></ul><ul class="list-unstyled" data-level="h3"><li data-target="#ref60668"><a class="w-100 link-gray-900" href="/science/population-biology-and-anthropology/Migration#ref60668">Forced migrations</a></li></ul><ul class="list-unstyled" data-level="h3"><li data-target="#ref60669"><a class="w-100 link-gray-900" href="/science/population-biology-and-anthropology/Migration#ref60669">Internal migrations</a></li></ul></li></ul><ul class="list-unstyled" data-level="h2"><li data-target="#ref60670"><a class="w-100 link-gray-900" href="/science/population-biology-and-anthropology/Natural-increase-and-population-growth">Natural increase and population growth</a><ul class="list-unstyled" data-level="h3"><li data-target="#ref60671"><a class="w-100 link-gray-900" href="/science/population-biology-and-anthropology/Natural-increase-and-population-growth#ref60671">Population growth</a></li></ul><ul class="list-unstyled" data-level="h3"><li data-target="#ref60672"><a class="w-100 link-gray-900" href="/science/population-biology-and-anthropology/Natural-increase-and-population-growth#ref60672">Population “momentum”</a></li></ul></li></ul></div></li><li data-target="#ref60673"><div class="d-flex align-items-center"><button class="h1-link-drawer-button btn btn-xs btn-circle d-flex rounded" type="button" aria-label="Toggle Heading"><em class="material-icons font-18" data-icon="keyboard_arrow_right"></em></button><a class="w-100 link-gray-900" href="/science/population-biology-and-anthropology/Natural-increase-and-population-growth#ref60673">Population composition</a></div><div class="ml-40 toc-drawer sub-toc-drawer"><ul class="list-unstyled" data-level="h2"><li data-target="#ref60674"><a class="w-100 link-gray-900" href="/science/population-biology-and-anthropology/Age-distribution">Age distribution</a></li></ul><ul class="list-unstyled" data-level="h2"><li data-target="#ref60675"><a class="w-100 link-gray-900" href="/science/population-biology-and-anthropology/Age-distribution#ref60675">Sex ratio</a></li></ul><ul class="list-unstyled" data-level="h2"><li data-target="#ref60676"><a class="w-100 link-gray-900" href="/science/population-biology-and-anthropology/Age-distribution#ref60676">Ethnic or racial composition</a></li></ul><ul class="list-unstyled" data-level="h2"><li data-target="#ref60677"><a class="w-100 link-gray-900" href="/science/population-biology-and-anthropology/Geographical-distribution-and-urbanization">Geographical distribution and urbanization</a></li></ul></div></li><li data-target="#ref60678"><div class="d-flex align-items-center"><button class="h1-link-drawer-button btn btn-xs btn-circle d-flex rounded" type="button" aria-label="Toggle Heading"><em class="material-icons font-18" data-icon="keyboard_arrow_right"></em></button><a class="w-100 link-gray-900" href="/science/population-biology-and-anthropology/Geographical-distribution-and-urbanization#ref60678">Population theories</a></div><div class="ml-40 toc-drawer sub-toc-drawer"><ul class="list-unstyled" data-level="h2"><li data-target="#ref60679"><a class="w-100 link-gray-900" href="/science/population-biology-and-anthropology/Geographical-distribution-and-urbanization#ref60679">Population theories in antiquity</a></li></ul><ul class="list-unstyled" data-level="h2"><li data-target="#ref60680"><a class="w-100 link-gray-900" href="/science/population-biology-and-anthropology/Geographical-distribution-and-urbanization#ref60680">Mercantilism and the idea of progress</a></li></ul><ul class="list-unstyled" data-level="h2"><li data-target="#ref60681"><a class="w-100 link-gray-900" href="/science/population-biology-and-anthropology/Geographical-distribution-and-urbanization#ref60681">Physiocrats and the origins of demography</a></li></ul><ul class="list-unstyled" data-level="h2"><li data-target="#ref60682"><a class="w-100 link-gray-900" href="/science/population-biology-and-anthropology/Geographical-distribution-and-urbanization#ref60682">Utopian views</a></li></ul><ul class="list-unstyled" data-level="h2"><li data-target="#ref60683"><a class="w-100 link-gray-900" href="/science/population-biology-and-anthropology/Malthus-and-his-successors">Malthus and his successors</a></li></ul><ul class="list-unstyled" data-level="h2"><li data-target="#ref60684"><a class="w-100 link-gray-900" href="/science/population-biology-and-anthropology/Malthus-and-his-successors#ref60684">Marx, Lenin, and their followers</a></li></ul><ul class="list-unstyled" data-level="h2"><li data-target="#ref60685"><a class="w-100 link-gray-900" href="/science/population-biology-and-anthropology/Malthus-and-his-successors#ref60685">The Darwinian tradition</a></li></ul><ul class="list-unstyled" data-level="h2"><li data-target="#ref60686"><a class="w-100 link-gray-900" href="/science/population-biology-and-anthropology/Malthus-and-his-successors#ref60686">Theory of the demographic transition</a></li></ul></div></li><li data-target="#ref60687"><div class="d-flex align-items-center"><button class="h1-link-drawer-button btn btn-xs btn-circle d-flex rounded" type="button" aria-label="Toggle Heading"><em class="material-icons font-18" data-icon="keyboard_arrow_right"></em></button><a class="w-100 link-gray-900" href="/science/population-biology-and-anthropology/Malthus-and-his-successors#ref60687">Trends in world population</a></div><div class="ml-40 toc-drawer sub-toc-drawer"><ul class="list-unstyled" data-level="h2"><li data-target="#ref60688"><a class="w-100 link-gray-900" href="/science/population-biology-and-anthropology/The-developing-countries-since-1950">The developing countries since 1950</a></li></ul><ul class="list-unstyled" data-level="h2"><li data-target="#ref60689"><a class="w-100 link-gray-900" href="/science/population-biology-and-anthropology/The-developing-countries-since-1950#ref60689">The industrialized countries since 1950</a></li></ul></div></li><li data-target="#ref60690"><div class="d-flex align-items-center"><div class="ml-25"></div><a class="w-100 link-gray-900" href="/science/population-biology-and-anthropology/Population-projections">Population projections</a></div><div class="ml-40 toc-drawer sub-toc-drawer"></div></li></ul> <a class="toc-extra-link link-gray-900" href="https://www.britannica.com/science/population-biology-and-anthropology/additional-info">References & Edit History</a> <a class="toc-extra-link link-gray-900" href="/facts/population-biology-and-anthropology">Related Topics</a> </div> <div class="tlr-media-slider pb-10 mb-30"> <a class="section-header link-gray-900 font-serif font-14 font-weight-bold mb-10 mx-10" href="https://www.britannica.com/science/population-biology-and-anthropology/images-videos">Images & Videos</a> <div class="slider 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Historical Debates, Current Controversies, and Implications for Understanding “Population Health” and Rectifying Health Inequities</a></li> <li><a class="external" href="https://pressbooks.pub/humangeography/chapter/2-1/" target="_blank" rel="noopener ">Pressbooks - Introduction to Human Geography - Population</a></li> <li><a class="external" href="https://pmc.ncbi.nlm.nih.gov/articles/PMC3722408/" target="_blank" rel="noopener ">National Center for Biotechnology Information - PubMed Central - Plum pomaces as a potential source of dietary fibre: composition and antioxidant properties</a></li> <li><a class="external" href="https://www.nature.com/scitable/knowledge/library/introduction-to-population-demographics-83032908/" target="_blank" rel="noopener ">Nature - Scitable - Introduction to Population Demographics</a></li> <li><a class="external" href="https://pressbooks.uwf.edu/envrioscience/chapter/4-3-the-human-population/" target="_blank" rel="noopener ">University of West Florida Pressbooks - Introduction to Environmental Sciences and Sustainability - Population</a></li> <li><a class="external" href="https://pressbooks.nscc.ca/introductiontosociology3rdedition/chapter/20-1-demography-and-population/" target="_blank" rel="noopener ">NSCC Libraries Pressbooks - Demography and Population</a></li> <li><a class="external" href="https://pressbooks.umn.edu/introbio/chapter/popdemographics/" target="_blank" rel="noopener ">University of Minnesota Libraries - Introductory Biology: Evolutionary and Ecological Perspectives - Demographics and Population Growth</a></li> <li><a class="external" href="https://bio.libretexts.org/Bookshelves/Introductory_and_General_Biology/General_Biology_1e_(OpenStax)/8%3A_Ecology/45%3A_Population_and_Community_Ecology/45.1%3A_Population_Demography" target="_blank" rel="noopener ">Biology LibreTexts - Population Demography</a></li> </ul> </div> <div class="md-websites-ebk-title">Britannica Websites</div> <div class="md-websites-ebk-subtitle">Articles from Britannica Encyclopedias for elementary and high school students.</div> <ul class="list-unstyled bps-topic-web-sites lh-lg"> <li><a class="external" href="https://kids.britannica.com/kids/article/population/625317" target="_blank" rel="noopener">population - Children's Encyclopedia (Ages 8-11)</a></li> <li><a class="external" href="https://kids.britannica.com/students/article/population/276507" target="_blank" rel="noopener">population - Student Encyclopedia (Ages 11 and up)</a></li> </ul> </div> </div> </div> </div> <div class="toc-header-marker"></div> <button class="ai-ask-button btn border-2 js-header-ai-ask-button d-none btn-sm btn-outline-red-400 border-red-400 mr-0 mr-lg-10 ml-5 ml-sm-10 ml-lg-0 p-10"> Ask the Chatbot a Question </button> <div class="md-byline module-spacing "> <div class="font-serif font-12"> <span class="written-by text-gray-700"> Written by </span> <div class="editor-popover popover p-0"> <a class="d-block p-20 gtm-byline font-12 byline-contributor" href="/contributor/Michael-S-Teitelbaum/2930" > <div class="editor-title font-16 font-weight-bold">Michael S. Teitelbaum</div> <div class="editor-description font-12 font-serif mt-5 clamp-description text-black">Program Officer, Alfred P. Sloan Foundation, New York City. Author of <i>The British Fertility Decline: Demographic Transition in the Crucible of the Industrial Revolution.</i></div> </a> <div data-popper-arrow></div> </div> <span class="btn btn-link editor-link p-0 qa-byline-link gtm-byline font-12 byline-contributor text-decoration-underline"> Michael S. Teitelbaum</span></div> <div class="font-serif font-12 text-gray-700"> <span class="qa-fact-checked-by">Fact-checked by</span> <div class="editor-popover popover p-0"> <a class="d-block p-20 font-12" href="/editor/The-Editors-of-Encyclopaedia-Britannica/4419" > <div class="editor-title font-16 font-weight-bold">The Editors of Encyclopaedia Britannica</div> <div class="editor-description font-12 font-serif mt-5 text-black">Encyclopaedia Britannica's editors oversee subject areas in which they have extensive knowledge, whether from years of experience gained by working on that content or via study for an advanced degree. They write new content and verify and edit content received from contributors.</div> </a> <div data-popper-arrow></div> </div> <span class="btn btn-link editor-link p-0 qa-byline-link font-12 "> The Editors of Encyclopaedia Britannica</span></div> <div class="last-updated font-12 font-serif"> <span class="text-gray-700"> Last Updated: <time datetime="2024-10-19T00:00:00CDT" >Oct 19, 2024</time> •</span> <a class="byline-edit-history" href="https://www.britannica.com/science/population-biology-and-anthropology/additional-info#history" rel="nofollow">Article History</a> </div></div> </div> <button class="d-flex d-lg-none btn btn-outline-blue border rounded-sm shadow-sm mobile-toc-button gtm-mobile-toc-inline-button d-none d-sm-block js-sections-inline-button module-spacing btn d-lg-none"> <em class="material-icons mr-5 ml-n10 my-n5 md-icon" data-icon="toc"></em> Table of Contents </button> <div class="d-flex d-sm-none flex-row"> <button class="d-flex d-lg-none btn btn-outline-blue border rounded-sm shadow-sm mobile-toc-button gtm-mobile-toc-inline-button js-sections-inline-button module-spacing"> <em class="material-icons mr-5 ml-n10 my-n5 md-icon" data-icon="toc"></em> Table of Contents </button> <button class="ai-ask-button btn border-2 ai-ask-button btn border-2 module-spacing btn-sm js-inline-ai-ask-button btn-outline-red-400 border-red-400 p-10 ml-5"> Ask the Chatbot a Question </button> </div> <div class="js-qf-module qf-module px-40 px-sm-20 py-15 mx-auto module-spacing font-14 bg-gray-50 rounded"> <div class="facts-list mt-10"> <div class=""> <div class="js-fact mb-10 line-clamp clamp-3"> <dl> <dt>Key People: </dt> <dd><a href="/biography/Charles-Darwin" topicid="151902">Charles Darwin</a></dd> <dd><a href="/biography/Charles-Elton" topicid="185326">Charles Elton</a></dd> <dd><a href="/biography/Nikolai-Vavilov" topicid="624223">Nikolai Vavilov</a></dd> <dd><a href="/biography/Kingsley-Davis" topicid="152804">Kingsley Davis</a></dd> <dd><a href="/money/Richard-Cantillon" topicid="93169">Richard Cantillon</a></dd> </dl> <button class="js-more-btn d-none btn btn-unstyled font-12 bg-gray-50" aria-label="Toggle more/less fact data"> <em class="js-content link-blue">(Show more)</em> </button> </div> </div> <div class=""> <div class="js-fact mb-10 line-clamp clamp-3"> <dl> <dt>Related Topics: </dt> <dd><a href="/science/minimum-viable-population" topicid="1933533">minimum viable population</a></dd> <dd><a href="/topic/population-pyramid" topicid="470464">population pyramid</a></dd> <dd><a href="/science/vital-rates" topicid="630912">vital rates</a></dd> <dd><a href="/science/age-distribution" topicid="8904">age distribution</a></dd> <dd><a href="/science/mortality-demography" topicid="393100">mortality</a></dd> </dl> <button class="js-more-btn d-none btn btn-unstyled font-12 bg-gray-50" aria-label="Toggle more/less fact data"> <em class="js-content link-blue">(Show more)</em> </button> </div> </div> <div class=""> <div class="js-fact mb-10 line-clamp clamp-3"> <dl> <dt>On the Web: </dt> <dd><a href="https://pmc.ncbi.nlm.nih.gov/articles/PMC3722408/" target="_blank">National Center for Biotechnology Information - PubMed Central - Plum pomaces as a potential source of dietary fibre: composition and antioxidant properties</a> (Nov. 22, 2024)</dd> </dl> <button class="js-more-btn d-none btn btn-unstyled font-12 bg-gray-50" aria-label="Toggle more/less fact data"> <em class="js-content link-blue">(Show more)</em> </button> </div> <div class="text-center"> <a class="btn btn-sm btn-link p-0" href="/facts/population-biology-and-anthropology"> See all related content </a> </div> </div> </div> </div><span class="marker before-article"></span><section data-level="1" id="ref1"><span class="marker PREMOD1 mod-inline"></span><p class="topic-paragraph"><strong><span id="ref377148"></span>population</strong>, in <a href="https://www.britannica.com/topic/human-being" class="md-crosslink " data-show-preview="true">human</a> <a href="https://www.britannica.com/science/biology" class="md-crosslink " data-show-preview="true">biology</a>, the <a href="https://www.britannica.com/science/natural-number" class="md-crosslink autoxref " data-show-preview="true">whole number</a> of inhabitants occupying an area (such as a <a href="https://www.britannica.com/topic/nation-state" class="md-crosslink autoxref " data-show-preview="true">country</a> or the world) and continually being modified by increases (births and <a href="https://www.britannica.com/topic/immigration" class="md-crosslink " data-show-preview="true">immigrations</a>) and losses (<a href="https://www.britannica.com/science/death" class="md-crosslink " data-show-preview="true">deaths</a> and emigrations). As with any biological population, the size of a human population is limited by the supply of food, the effect of <a href="https://www.britannica.com/science/human-disease" class="md-crosslink " data-show-preview="true">diseases</a>, and other environmental factors. Human populations are further affected by social customs governing reproduction and by the technological developments, especially in <a href="https://www.britannica.com/science/medicine" class="md-crosslink " data-show-preview="true">medicine</a> and <a href="https://www.britannica.com/topic/public-health" class="md-crosslink autoxref " data-show-preview="true">public health</a>, that have reduced <a href="https://www.britannica.com/science/mortality-demography" class="md-crosslink autoxref " data-show-preview="true">mortality</a> and extended the life span.</p><span class="marker MOD1 mod-inline"></span><span class="marker PREMOD2 mod-inline"></span><p class="topic-paragraph">Few aspects of human societies are as fundamental as the size, <a class="md-dictionary-link md-dictionary-tt-off mw" data-term="composition" href="https://www.merriam-webster.com/dictionary/composition" data-type="MW">composition</a>, and rate of change of their populations. Such factors affect economic prosperity, <a href="https://www.britannica.com/topic/health" class="md-crosslink autoxref " data-show-preview="true">health</a>, education, family structure, crime patterns, language, culture—indeed, virtually every aspect of human society is touched upon by population trends.</p><span class="marker MOD2 mod-inline"></span><span class="marker PREMOD3 mod-inline"></span><div class="assemblies"><div class="w-100"><figure class="md-assembly m-0 mb-md-0 card card-borderless print-false" data-assembly-id="277390" data-asm-type="video"><div class="md-assembly-wrapper card-media " data-type="video" video-id="237629"><a data-id="237629" class="gtm-assembly-link d-flex justify-content-center" style="--aspect-ratio: 16/9" href="/video/population-overpopulation/-277390"><img src="https://cdn.britannica.com/29/237629-138-BA069DE3/population-overpopulation.jpg?w=800&h=450&c=crop" alt="Is overpopulation a problem?" loading="lazy"><script type="application/json"> { "sources": [ { "file" : "//content.jwplatform.com/manifests/pD6n0NwF.m3u8" } ], "image": "https://cdn.britannica.com/29/237629-138-BA069DE3/population-overpopulation.jpg" ,"tracks": [ { "file" : "//assets-jpcust.jwpsrv.com/tracks/h3tet02P", "label": "English" } ] ,"adfile": "//content.jwplatform.com/manifests/fxgZlWNs.m3u8" } </script><div class="btn btn-xl btn-white btn-circle position-absolute shadow" style="top: 50%; transform: translateY(-50%)"><em class="material-icons" data-icon="play_arrow"></em></div></a></div><figcaption class="card-body"><div class="md-assembly-caption text-muted font-14 font-serif line-clamp"><span><span class="md-assembly-title font-weight-bold mr-5 d-inline font-sans-serif md-video-caption" video-control="237629">Is overpopulation a problem?</span><span>On November 15, 2022, the United Nations declared that the world's population had reached eight billion people.</span><button class="js-more-btn d-none btn btn-unstyled font-12 bg-white js-content" aria-label="Toggle more/less fact data"><span class="link-blue">(more)</span></button></span></div><a class="font-14 mt-10 d-inline-block" href="/science/population-biology-and-anthropology/images-videos">See all videos for this article</a></figcaption></figure></div></div><p class="topic-paragraph">The study of human populations is called <span id="ref366870"></span><a href="https://www.britannica.com/topic/demography" class="md-crosslink " data-show-preview="true">demography</a>—a <a class="md-dictionary-link md-dictionary-tt-off mw" data-term="discipline" href="https://www.merriam-webster.com/dictionary/discipline" data-type="MW">discipline</a> with <a class="md-dictionary-link md-dictionary-tt-off mw" data-term="intellectual" href="https://www.merriam-webster.com/dictionary/intellectual" data-type="MW">intellectual</a> origins stretching back to the 18th century, when it was first recognized that human mortality could be examined as a phenomenon with statistical regularities. Especially influential was English economist and <a href="https://www.britannica.com/topic/demography" class="md-crosslink " data-show-preview="true">demographer</a> <a href="https://www.britannica.com/money/Thomas-Malthus" class="md-crosslink " data-show-preview="true">Thomas Malthus</a>, who is best known for his theory that <a href="https://www.britannica.com/science/population-growth" class="md-crosslink autoxref " data-show-preview="true">population growth</a> will always tend to outrun the food supply and that betterment of humankind is impossible without stern limits on reproduction. This thinking is commonly referred to as <a href="https://www.britannica.com/money/Malthusianism" class="md-crosslink " data-show-preview="true">Malthusianism</a>.</p><span class="marker MOD3 mod-inline"></span><span class="marker PREMOD4 mod-inline"></span><p class="topic-paragraph"><em><a href="https://www.britannica.com/topic/Thomas-Malthus-on-population-1987927" class="md-crosslink " data-show-preview="true">(Read Thomas Malthus’s 1824 Britannica essay on population.)</a></em></p><span class="marker MOD4 mod-inline"></span><span class="marker PREMOD5 mod-inline"></span><p class="topic-paragraph">Demography casts a multidisciplinary net, drawing insights from <a href="https://www.britannica.com/money/economics" class="md-crosslink " data-show-preview="true">economics</a>, <a href="https://www.britannica.com/topic/sociology" class="md-crosslink " data-show-preview="true">sociology</a>, <a href="https://www.britannica.com/science/statistics" class="md-crosslink " data-show-preview="true">statistics</a>, medicine, <a href="https://www.britannica.com/science/biology" class="md-crosslink " data-show-preview="true">biology</a>, <a href="https://www.britannica.com/science/anthropology" class="md-crosslink " data-show-preview="true">anthropology</a>, and history. Its chronological sweep is lengthy: limited <a class="md-dictionary-link md-dictionary-tt-off mw" data-term="demographic" href="https://www.merriam-webster.com/dictionary/demographic" data-type="MW">demographic</a> evidence for many centuries into the past, and reliable data for several hundred years are available for many regions. The present understanding of demography makes it possible to project (with caution) population changes several decades into the future.</p><a class="link-module shadow-sm d-block qa-quiz-module" href="/quiz/which-country-is-larger-by-population-quiz" data-link-module-iframe-link=""> <img loading="lazy" src="https://cdn.britannica.com/91/142291-131-1FF39F2D/Flags-world-blue-sky-Countries-Globalization-relations-2010.jpg" alt="Flags of the world against blue sky. Countries, International. Globalization, global relations, Australia, Canada, United Kingdom, Poland, Palestine, Japan. Homepage 2010, arts and entertainment, history and society" class="rounded-sm mr-15" width="70" /> <div class="line-clamp clamp-5"> <div class="module-title bg-green">Britannica Quiz</div> <div class="font-weight-semi-bold mt-5">Which Country Is Larger By Population? Quiz</div> </div> </a><span class="marker MOD5 mod-inline"></span></section> <span class="marker h2"></span><section data-level="1" id="ref60653"> <h2 class="h1">The basic components of population change</h2> <span class="marker PREMOD6 mod-inline"></span><p class="topic-paragraph">At its most basic level, the components of population change are few indeed. A <span id="ref366871"></span><a href="https://www.britannica.com/topic/closed-population" class="md-crosslink ">closed population</a> (that is, one in which immigration and emigration do not occur) can change according to the following simple equation: the population (closed) at the end of an interval equals the population at the beginning of the interval, plus births during the interval, minus deaths during the interval. In other words, only addition by births and reduction by deaths can change a closed population.</p><span class="marker MOD6 mod-inline"></span> <span class="marker PREMOD7 mod-inline"></span><p class="topic-paragraph">Populations of nations, regions, continents, islands, or cities, however, are rarely closed in the same way. If the assumption of a closed population is relaxed, in- and out-migration can increase and decrease population size in the same way as do births and deaths; thus, the population (open) at the end of an interval equals the population at the beginning of the interval, plus births during the interval, minus deaths, plus in-migrants, minus out-migrants. Hence the study of demographic change requires knowledge of fertility (births), mortality (deaths), and <a href="https://www.britannica.com/science/migration-animal" class="md-crosslink autoxref " data-show-preview="true">migration</a>. These, in turn, affect not only population size and growth rates but also the composition of the population in terms of such attributes as <a href="https://www.britannica.com/science/sex" class="md-crosslink autoxref " data-show-preview="true">sex</a>, age, ethnic or racial composition, and geographic distribution.</p><div class="module-spacing"> <DIV class="marketing-INLINE_SUBSCRIPTION marketing-content" data-marketing-id="INLINE_SUBSCRIPTION"><style> .student-promo-banner-wrapper { container-type: inline-size; margin-bottom: 15px; } @container (min-width: 475px) { .student-promo-banner { flex-direction: row; } .student-promo-banner-img-wrapper { margin-bottom: 0; margin-right: 10px; justify-content: flex-start; } .student-promo-banner-text-wrapper { text-align: left; margin-bottom: 0px; margin-left: 10px; } .student-promo-banner-button-wrapper { margin-right: 0; } }</style> <div class="student-promo-banner-wrapper"> <div class="student-promo-banner d-flex flex-column align-items-center bg-blue rounded p-20"> <div class="student-promo-banner-img-wrapper mb-20 mr-0 d-flex justify-content-center"> <img class="rounded" style="max-width: 100px; min-width: 80px" src="https://cdn.britannica.com/marketing/BlueThistle.webp" /> </div> <div class="student-promo-banner-text-wrapper ml-0 mb-10 text-center text-white"> <div class="h2 mb-10">Get Unlimited Access</div> <div class="h4 font-weight-semi-bold">Try Britannica Premium for free and discover more.</div> </div> <div class="student-promo-banner-button-wrapper d-flex justify-content-center align-items-center ml-auto mr-auto"> <a class="btn btn-m btn-orange" href="https://premium.britannica.com/premium-membership/?utm_source=premium&utm_medium=inline-cta&utm_campaign=black-friday-2024">Subscribe</a> </div> </div> </div> </DIV></div><span class="marker MOD7 mod-inline"></span> <section data-level="2" id="ref60654"> <h2 class="h2"><span id="ref366872"></span><a href="https://www.britannica.com/science/fertility" class="md-crosslink " data-show-preview="true">Fertility</a></h2> <span class="marker PREMOD8 mod-inline"></span><p class="topic-paragraph">Demographers distinguish between fecundity, the underlying biological potential for reproduction, and fertility, the actual level of achieved reproduction. (Confusingly, these English terms have opposite meanings from their parallel terms in French, where <em>fertilité</em> is the potential and <em>fécondité</em> is the realized; similarly <a class="md-dictionary-link md-dictionary-tt-off mw" data-term="ambiguous" href="https://www.merriam-webster.com/dictionary/ambiguous" data-type="MW">ambiguous</a> usages also prevail in the biological sciences, thereby increasing the chance of misunderstanding.) The difference between biological potential and realized fertility is determined by several intervening factors, including the following: (1) most women do not begin reproducing immediately upon the onset of puberty, which itself does not occur at a fixed age; (2) some women with the potential to reproduce never do so; (3) some women become widowed and do not remarry; (4) various elements of social behaviour restrain fertility; and (5) many human couples choose consciously to restrict their fertility by means of <a href="https://www.britannica.com/topic/celibacy" class="md-crosslink autoxref " data-show-preview="true">sexual abstinence</a>, contraception, abortion, or sterilization.</p><span class="marker MOD8 mod-inline"></span> <span class="marker PREMOD9 mod-inline"></span><p class="topic-paragraph">The magnitude of the gap between potential and realized fertility can be illustrated by comparing the highest known fertilities with those of typical European and North American women in the late 20th century. A well-studied high-fertility group is the <span id="ref366873"></span><a href="https://www.britannica.com/topic/Hutterites" class="md-crosslink " data-show-preview="true">Hutterites</a> of <a href="https://www.britannica.com/place/North-America" class="md-crosslink autoxref " data-show-preview="true">North America</a>, a religious sect that views fertility regulation as sinful and high fertility as a blessing. Hutterite women who married between 1921 and 1930 are known to have averaged 10 children per woman. Meanwhile, women in much of Europe and North America averaged about two children per woman during the 1970s and 1980s—a number 80 percent less than that achieved by the Hutterites. Even the highly fertile populations of <span id="ref366874"></span><a href="https://www.britannica.com/money/developing-country" class="md-crosslink " data-show-preview="true">developing countries</a> in Africa, Asia, and Latin America produce children at rates far below that of the Hutterites.</p><span class="marker MOD9 mod-inline"></span> <span class="marker PREMOD10 mod-inline"></span><p class="topic-paragraph">The general message from such evidence is clear enough: in much of the world, human fertility is considerably lower than the biological potential. It is strongly <a class="md-dictionary-link md-dictionary-tt-off eb" data-term="constrained" href="https://www.britannica.com/dictionary/constrained" data-type="EB">constrained</a> by cultural regulations, especially those concerning marriage and sexuality, and by conscious efforts on the part of married couples to limit their childbearing.</p><span class="marker MOD10 mod-inline"></span> <span class="marker PREMOD11 mod-inline"></span><p class="topic-paragraph">Dependable evidence on historical fertility patterns in <span id="ref366875"></span><a href="https://www.britannica.com/place/Europe" class="md-crosslink " data-show-preview="true">Europe</a> is available back to the 18th century, and estimates have been made for several earlier centuries. Such data for non-European societies and for earlier human populations are much more fragmentary. The European data indicate that even in the absence of widespread deliberate regulation there were significant variations in fertility among different societies. These differences were heavily affected by <span id="ref366876"></span><a href="https://www.britannica.com/topic/human-social-behaviour" class="md-crosslink ">socially determined behaviours</a> such as those concerning marriage patterns. Beginning in France and Hungary in the 18th century, a dramatic decline in fertility took shape in the more developed societies of Europe and North America, and in the ensuing two centuries fertility declines of fully 50 percent took place in nearly all of these countries. Since the 1960s fertility has been intentionally diminished in many developing countries, and remarkably rapid reductions have occurred in the most populous, the <a href="https://www.britannica.com/place/China" class="md-crosslink autoxref " data-show-preview="true">People’s Republic of China</a>.</p><div class="one-good-fact-module"> </div><span class="marker MOD11 mod-inline"></span> <span class="marker PREMOD12 mod-inline"></span><p class="topic-paragraph">There is no dispute as to the fact and magnitudes of such declines, but theoretical explanation of the phenomena has proved <a class="md-dictionary-link md-dictionary-tt-off mw" data-term="elusive" href="https://www.merriam-webster.com/dictionary/elusive" data-type="MW">elusive</a>. (See below <a href="https://www.britannica.com/science/population-biology-and-anthropology/Geographical-distribution-and-urbanization#ref60678" class="md-crosslink " data-show-preview="true">Population theories</a>.)</p><span class="marker MOD12 mod-inline"></span> </section></section><span class="marker end-of-content"></span><span class="marker after-article"></span></div> <div id="chatbot-root"></div> </div> </div> </div> <div class="ai-dialog-placeholder"></div> </div> </div> <aside class="col-md-da-320"></aside> </div> </div> </div> </div> </article></div> </div></div> </div> </main> <div id="md-footer"></div> <noscript><iframe src="//www.googletagmanager.com/ns.html?id=GTM-5W6NC8" height="0" width="0" style="display:none;visibility:hidden"></iframe></noscript> <script type="text/javascript" id="_informizely_script_tag"> var IzWidget = IzWidget || {}; (function (d) { var scriptElement = d.createElement('script'); scriptElement.type = 'text/javascript'; scriptElement.async = true; scriptElement.src = "https://insitez.blob.core.windows.net/site/f780f33e-a610-4ac2-af81-3eb184037547.js"; var node = d.getElementById('_informizely_script_tag'); node.parentNode.insertBefore(scriptElement, node); } )(document); </script>  <script> window.ap3c = window.ap3c || {}; var ap3c = window.ap3c; ap3c.cmd = ap3c.cmd || []; ap3c.cmd.push(function() { ap3c.init('ZO4siT4cLwnykPnzZWJtd3Byb2Q', 'https://engage.email.britannica.com/'); ap3c.track({v: 0}); }); ap3c.activity = function(act) { ap3c.act = (ap3c.act || []); ap3c.act.push(act); }; var s, t; s = document.createElement('script'); s.type = 'text/javascript'; s.src = "https://engage.email.britannica.com/app.js"; t = document.getElementsByTagName('script')[0]; t.parentNode.insertBefore(s, t); </script> <script class="marketing-page-info" type="application/json"> {"pageType":"Topic","templateName":"DESKTOP","pageNumber":1,"pagesTotal":10,"pageId":470303,"pageLength":1020,"initialLoad":true,"lastPageOfScroll":false} </script> <script class="marketing-content-info" type="application/json"> [] </script> <script src="https://cdn.britannica.com/mendel-resources/3-130/js/libs/jquery-3.5.0.min.js?v=3.130.14"></script> <script type="text/javascript" data-type="Init Mendel Code Splitting"> (function() { $.ajax({ dataType: 'script', cache: true, url: 'https://cdn.britannica.com/mendel-resources/3-130/dist/topic-page.js?v=3.130.14' }); })(); </script> <script class="analytics-metadata" type="application/json"> {"leg":"D","adLeg":"D","userType":"ANONYMOUS","pageType":"Topic","pageSubtype":null,"articleTemplateType":"PAGINATED","gisted":false,"pageNumber":1,"hasSummarizeButton":false,"hasAskButton":false} </script> <script type="text/javascript"> EBStat={accountId:-1,hostnameOverride:'webstats.eb.com',domain:'www.britannica.com', json:''}; </script> <script type="text/javascript"> ( function() { $.ajax( { dataType: 'script', cache: true, url: '//www.britannica.com/webstats/mendelstats.js?v=1' } ) .done( function() { try {writeStat(null,EBStat);} catch(err){} } ); })(); </script> <div id="bc-fixed-dialogue"></div> </body> </html>

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Population | Definition, Trends, & Facts | Britannica