Industrialization: Demographic Transition Theory

This article is an overview of demographic transition theory. It outlines the differences between the four main stages of the demographic transition and explains what factors help countries move from one stage to the next. It also considers whether some developed nations have moved into a fifth stage of the demographic transition (in which population will decline) and discusses some of the consequences of such a change in terms of the economy and immigration. Population pyramids as a research tool for studying the demographic transition are presented, as is a discussion of trends in global population change. Finally, the article discusses current controversies around the continuing applicability of demographic transition theory to less-developed countries in a time of HIV and other global epidemics as well as continued global population growth.

Demographic transition theory refers to a mathematical model which explains the change in demographic trends as countries move from preindustrial to industrialized economies. The model is based on work observing demographic changes which was begun in 1929 by Warren Thompson, a foundational American demographer. It is important to note that this model is only an idealized picture of how demographic change has occurred; it does not necessarily apply completely to all individual countries. The basic premise of demographic transition theory is that nations go through four stages as they transition from preindustrial to industrialized economies.

Stage One

The first stage of the demographic transition corresponds to pre-industrialized, or pre-modern, societies. In such societies, both birth and death rates are high. Children are valuable economic actors in society, often performing many household tasks as well as contributing to the agricultural or craft labor that sustains the household. When they reach adulthood, children in premodern societies support their parents, as there is no social safety net and no organized retirement savings. In addition, the lack of medical care and sanitation technology means that disease is rampant and death in childbirth is likely. Famines and epidemics periodically cause marked population declines. Because children are so valuable in premodern societies yet simultaneously so unlikely to survive, people have many children. Yet because of the high death rate, additions to and subtractions from the population tend to even out. In fact, until the Middle Ages, world population growth averaged less than 0.05% a year and it took between one thousand and five thousand years for the population to double.

Stage Two

In the second stage, the population begins to increase at a much faster rate. This is caused by a decline in death rates while birth rates remain high. The decline in death rates occurs for two primary reasons. First of all, improvements in agricultural production, such as those initiated during the Agricultural Revolution in eighteenth century Europe, lead to a more stable and productive food supply. A stable and productive food supply reduces deaths that are a consequence of famine. Second, there are significant advances in public health technology, particularly sanitation, hygiene, and food handling. For instance, cities built sewerage systems that reduced contamination of drinking water supplies and indoor plumbing began to make regular bathing a possibility. Nations that have experienced a demographic transition more recently might also experience improvements in medical care at the same time as improvements in public health technology; in Europe medical care remained quite primitive throughout the second stage of the demographic transition.

During the second stage, the population grows rapidly in a process that demographers call a population explosion. The exact rate of growth varies depending on the society in question, but the growth takes on a common pattern. In particular, the public health advances that are part of the second stage of the demographic transition tend not to increase the lifespan. Instead, they decrease the risk that children will die before they reach adulthood and become able to have their own children. Therefore, more and more people have children, leading not only to an exponential increase in the rate of population growth but also to an age structure in which younger people predominate.

Stage Three

In the third stage of the demographic transition, the population becomes more stable and eventually begins to decline. This decline occurs through the reduction of birth rates, leading to a changed population structure in which there are fewer young people and more old people. However, before the population of old people rises, there is a period of economic opportunity and expansion as more individuals are of working age and fewer are either in childhood or old age.

Demographers and other social scientists debate which factors are most important in producing the changes observed in the third stage. There are five common explanations that are given for the reduction in the birth rate:

• Parents may observe the decline in childhood death rates and determine that they do not need to have as many children as before in order to assure enough household labor and sufficient support in old age.
• Political changes that reduce children's ability to legally earn a wage outside of the home and require parents to pay for clothing and education for their children cause children to be expensive rather than productive members of families.
• When the availability of and knowledge about contraceptive use increase, it gives people the ability to plan childbearing.
• When literacy and employment rates for women rise, women gain more control over their lives and thus their fertility. In addition, women who are working outside the home have less time to raise children.
• Increasing rates of urbanization lead to families who live in smaller spaces and have less need for household labor, increasing the cost and decreasing the utility of extra family members.

Stage Four

The fourth stage of the demographic transition occurs when both birth and death rates are low. In such societies, the population has become quite large, but its size remains stable over time. This occurs when the fertility rate falls below replacement levels, or about 2.1 children per woman. It is important to note that not all societies transition from the third stage to the fourth stage. Nations that are in the fourth stage include the United States, Canada, Australia, most of Europe, several of the more developed nations in Latin America, and the nations of East Asia. Such societies have reaped the benefits of improved agricultural technology, public health measures, and now medical care that allow for massive declines in the death rate, but have not seen corresponding decreases in the birth rate. Such a situation is likely to occur in nations that restrict literacy and employment opportunities for their citizens, especially women; where there are strong religious reasons to continue bearing children at high rates; and where periodic famines or civil wars lead families to believe their children are still at risk. Most of the developing world has not yet reached stage four; however, significant changes have occurred in many Latin American, Asian, and North African nations. In contrast, some Middle Eastern and sub-Saharan African nations have seen fertility rate declines as small as 10 percent.

Population Decline & Immigration

As it was originally developed, demographic transition theory contained only the four stages outlined above. However, some demographers have argued that a fifth stage is necessary in order for the explanation to be complete. In this fifth stage, fertility rates fall beneath replacement level and thus -- at least in the absence of immigration -- the total population of a nation begins to fall. Nations that currently have fertility rates below replacement levels and which are beginning to see population declines include Japan and the European countries on the Mediterranean.

According to the CIA World Factbook, the 2008 fertility rate in the United States was 2.1, putting it just at replacement level. If the fertility rate were to be calculated only for individuals born in the United States, it would be significantly lower, putting the United States in the company of Japan and Italy with declining populations. The CIA World Factbook's 2013 population growth rate estimate was just 0.9 percent. However, the United States population is still growing, albeit slowly. In 2012 the U.S. Census Bureau projected that the US population would grow from 314 million in 2012 to 399.8 million in 2050, while Japan's population is expected to drop from 127.6 million in 2012 to 95.5 million in 2050 (U.S. Census Bureau, 2012; Demetriou, 2013).What makes the difference is immigration. First of all, immigrants themselves increase national populations even in the absence of any effect on fertility rates. Secondly, immigrants tend to have children at about the same rate or only have slightly fewer than they would have had in their sending country. This means that in the United States, where women born in the country give birth to fewer than two children per woman on average, immigrant women often give birth to many more.

The higher fertility rates of immigrant women often worry forces opposed to immigration. However, declining populations that are simultaneously aging can have detrimental effects on the economy. When fewer people are working, it leads to a decline in a nation's gross domestic product (GDP). Additionally, a smaller working population coupled with a larger elderly population can strain the social safety net, and such trends are part of the reason why some political and economic analysts worry about the future of Social Security (in the United States) and similar programs. In fact, some European nations have begun considering how they can increase immigration in order to deal with the economic crises that arise from the aging and declining population. In any case, it is immigrants and their fertility that keeps the United States in stage four rather than stage five of the demographic transition.

Despite the declines in population in some developed countries, the world as a whole remains in the second stage of the demographic transition. Rates of growth have declined since their peak in the late 1980s, but the current world population growth rate is still above 1%, representing a period of only about four decades for a doubling of the global population. At this rate, the world population is expected to reach 9 billion by 2044; it was only 3 billion in 1959. While the United States Census Bureau projects that by 2050, the rate of global population growth will have fallen to 0.5% a year, this will still represent an increase of about 900 million people per year and will keep the world firmly planted in the second phase of the demographic transition (U.S. Census Bureau, 2008; 2011).

Applications

Population Pyramids

Besides simply calculating birth rates, death rates, fertility rates, and rates of population growth or decline for different countries, one of the main ways that demographers determine which stage of the demographic transition an individual nation is currently in is by creating what is known as a population pyramid. Population pyramids are based on bar graphs. On the y-axis (the vertical axis), bars are made for different age groups. On either side of the y-axis, the x-axis (the horizontal axis) represents the number of individuals of that age group in the population. Conventionally, the left side of the graph represents males and the right side represents females. There are many things that demographers can learn from population pyramids. For instance, they can learn if men or women are living longer, if there is some kind of event in young adulthood that is depressing the number of men or women, and if nations have experienced a "youth bulge" (Fuller, 1995), or a situation in which the number of young people has expanded considerably. Demographers also look at the shape of a population pyramid to determine which phase of the demographic transition a nation is in during the time period the pyramid represents. Figure 1 below shows the shapes of population pyramids for the first four stages of the demographic transition; the fifth stage would begin to resemble an inverted pyramid.

Of course, not all nations have population pyramids that resemble one of these standard models. For instance, the estimated population pyramid of the United States in 2013 resembles a combination of a Stage 1 pyramid and a Stage 3 pyramid (CIA World Factbook, 2013). The top portion of the pyramid, representing people who were aged fifty and older in 2013, resembles a Stage 1 pyramid. The large base of this top portion is the baby boom generation. Below the baby boom generation, the population of people in their thirties is a bit smaller, like the top of a Stage 3 pyramid. Despite some dips and upswings, the total population aged zero to twenty-five has remained fairly stable.

Viewpoints

Is Demographic Transition Theory Still Accurate?

There are a number of differences between the way that the demographic transition occurred in European nations and the way it has happened in less-developed countries. Four of these differences are most important. First of all, the demographic transition occurred later in less-developed countries. This is not surprising, given that agricultural and public health technology reached such nations much later than it reached Europe. Second, the decline in death rates in less-developed countries occurred much more rapidly. This decline has occurred for a number of reasons. Unlike in Europe, where technological improvements in agriculture and public health had to be slowly developed and implemented over time, such improvements could be imported relatively rapidly in less-developed countries that imported technologies from Europe or the United States. Less-developed countries were able to couple their agricultural and public health improvements with advances in medical care that saved many lives. Improved access to contraceptive technology as well as to literacy education for women led to behavioral changes in less-developed countries during stage two that in Europe did not occur until stage three. Third, the time between when the death rates began to fall and when the birth rates began to fall has been much longer in less-developed countries. This is partially due to the lower rates of urbanization in many less-developed countries; the fact that morality and religion play a larger role in regulating fertility than in regulating mortality may also play a role. Finally, less-developed countries developed much higher fertility rates than developed countries ever did, leading to an age structure that is extremely young. The consequence of this is that even in countries that have begun to see a decline in the number of births per woman, the population will continue to increase due to the growing numbers of women giving birth.

All of these observations lead to an important question: is demographic transition theory applicable to less-developed countries at all? Some analysts argue that demographic transition theory is just an attempt to generalize to all countries based on Europe's experience. To these analysts, Europe followed one path through history and other countries may follow quite different paths. History is not linear or predictable. Other analysts point to specific data and trends that the demographic transition theory model has not incorporated and which limit its applicability to less-developed countries. For instance, significant wealth, urbanization, and female literacy have not led to declines in the fertility rate in all countries. Government policies and religious ideals can lead to continued high fertility even where indicators might predict a decline.

Another example of trends that are not incorporated into the demographic transition theory model is the rise of HIV and other modern epidemics. Despite modern public health measures and modern medical developments, HIV and some other illnesses remain major causes of death across the world, particularly in less-developed countries. In some areas of Africa, about one-third of all people are HIV positive. Though individuals with HIV can and do have children before dying of the disease, their children are unlikely to survive to adulthood and to reproduce themselves without costly drug therapies that remain unavailable in less-developed countries. HIV, in consequence, turns the demographic transition model on its head by increasing death rates in societies that had already entered stage two of the model.

Terms & Concepts

Birth Rate: The birth rate is the ratio between the number of births to members of a population and the total number of individuals in that population over a specified period of time.

Death Rate: The death rate is the ratio between the number of deaths of members of a population and the total number of individuals in that population over a specified period of time.

Demography: Demography is the study of population characteristics such as size, growth or decline rates, age structures, and distribution. Individuals who work in the field of demography are called demographers.

Development: Development refers to the process of national economic growth and modernization.

Epidemic: An epidemic is an incidence of a contagious disease in which new cases appear in the population at a rate greatly exceeding that which medical experts expect given past transmission rates. Epidemics usually occur for diseases that transmit easily. While any sort of disease can have an epidemic, people are most concerned about epidemics that occur for diseases that are highly fatal. Examples of epidemics include the Black Death in Europe in the Middle Ages, the flu pandemic in 1918, and HIV/AIDS in sub-Saharan Africa today.

Famine: A severe shortage of food in a given area that results in extreme hunger, starvation, and often large numbers of deaths. Famines can occur for a variety of reasons, including crop failure due to weather conditions or pests as well as due to political instability affecting food distribution patterns.

Fertility Rate: The fertility rate is the number of live births that occur per 1,000 women of reproductive age in a given year. Women of reproductive age are generally considered to be those between ages fifteen and forty-four, though some births do occur to younger or older women.

Gross Domestic Product (GDP): The total market value of all goods and services produced by an individual nation's economy during a specific year.

Industrialization: Industrialization is the process of moving from an agricultural to an industrial economic system. The main components of industrialization are the development of organized systems of labor and production that result in work outside the home to produce saleable goods for a market economy. Industrialization in developed countries occurred during the Industrial Revolution in the late eighteenth and early nineteenth centuries, when factory production was invented; industrialization is still occurring in many less-developed countries. However, most developed countries are currently seeing a transition to post-industrial economies where services rather than goods are produced.

Less-Developed Countries: Less-developed countries are those with low incomes per person and low levels of industrialization. Most less-developed countries are located in the global south, including in Asia, Africa, and Latin America. Historically, the term "third world" was often used to refer to less-developed nations, but this usage has fallen out of favor with academics and the term is best avoided unless it is used to refer to neutral and nonaligned countries during the Soviet era.

Sending Country: The country from which an immigrant comes.

Urbanization: The process whereby larger proportions of the population come to live and work in cities and where cities themselves grow larger.

Bibliography

Caldwell, J.C. (2006). Demographic Transition Theory. Dordecht, Netherlands: Springer.

Central Intelligence Agency. (2008). United States. The World Factbook. Accessed August 27, 2008 from https://www.cia.gov/library/publications/the-world-factbook/geos/us.html

Central Intelligence Agency (2013). United States. The World Factbook.Retrieved November 6, 2013 from https://www.cia.gov/library/publications/the-world-factbook/geos/us.html

Demetriou, D. (2013). Japan's population suffers biggest fall in history. Telegraph. Retrieved November 6, 2013 from http://www.telegraph.co.uk/news/worldnews/asia/japan/9999591/Japans-population-suffers-biggest-fall-inhistory.html

Fuller, G. (1995). The demographic backdrop to ethnic conflict: A geographic overview. In Central Intelligence Agency. The Challenge of Ethnic Conflict to National and International Order in the 1990s: Geographic Perspectives. 151-54. Washington, DC: Central Intelligence Agency.

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Suggested Reading

Bras, H., Van Bavel, J., & Mandemakers, K. (2013). Unraveling the intergenerational transmission of fertility: Genetic and shared-environment effects during the demographic transition in the Netherlands, 1810-1910. History Of The Family (Elsevier Science), 18(2), 116-134. Retrieved November 6, 2013 from EBSCO Online Database SocINDEX with Full Text. http://search.ebscohost.com/login.aspx?direct=true&db=sih&AN=90289759

Caldwell, J. (2008). Three fertility compromises and two transitions. Population Research & Policy Review 27(4), 427-446. Retrieved August 28, 2008 from EBSCO online database SocINDEX with Full Text, http://search.ebscohost.com/login.aspx?direct=true&db=sih&AN=32762882&site=ehost-live.

Ehmer, J. (2011). The significance of looking back: Fertility before the "fertility decline.". Historical Social Research, 36(2), 11-34. Retrieved November 6, 2013 from EBSCO Online Database SocINDEX with Full Text. http://search.ebscohost.com/login.aspx?direct=true&db=sih&AN=59158762

Fehr, H., Jokisch, S., & Kotlikoff, L.J. (2008). Fertility, mortality, and the developed world's demographic transitions. Journal of Policy Modeling 30(3), 455-73.

Kahn, A. (2008). The industrial revolution and the demographic transition. Business Review of the Federal Reserve Bank of Philadelphia. First Quarter. 9-15. Retrieved August 28, 2008 from EBSCO online database Academic Search Premier, http://search.ebscohost.com/login.aspx?direct=true&db=aph&AN=32061685&site=ehost-live

Kirk, D. (1996). Demographic transition theory. Population Studies 50(3), 361-87.

Stauffer, C. (1999). Building pyramids. Population Today, 27(5), 3.

United States Census Bureau. 2004. Global Population Composition. Accessed August 28, 2008 from http://www.census.gov/ipc/prod/wp02/wp-02004.pdf