(February 2013) To give people a clear and compelling picture of world population, demographers have a favorite graphic—the population pyramid. It looks like its name: a very broad base that comes to a point at the top. Ages are displayed as groupings (for example, 0 to 4, 5 to 9), and the pyramid has two sides—one for males and one for females. But for many countries, a pillar and not a pyramid is the accurate graphic.

Look at the pyramid below that displays the population of the developing countries.1 The expanding base shows a large "young" population because women in most developing countries currently average around 2.4 children each.2 Replacement-level fertility (around 2.1 children per woman) eventually results in little if any population growth: A couple who has only two children in effect "replaces" itself. But with a higher birth rate, each generation increases in size and the pyramid continues to grow in size and widen. The pyramid narrows toward the top because of a smaller number of births many years in the past (the population size was much smaller) and because of higher death rates at older ages.

Now click the radio button for the developed countries. Quite a stark contrast! The wide base is long gone and unlikely ever to return. Notice also that the pyramids are displayed in numbers (population in millions) and that the scales for the two pyramids are the same, showing both population size and the composition by age groups and sex. Women in developed countries average 1.6 children each and, as a group, have been below the "replacement" level since 1975—quite a long time.

This new "pillar" form of the traditional population pyramid has far more significance than a simple change in the shape of a graph. It represents a new form of society that is emerging worldwide. The causes vary to some degree from country to country but, by and large, are a result of changed attitudes of younger generations towards life's fundamental stages: taking one's place in the labor force; views on the necessity of marriage; improved contraception; and weighing the costs, benefits, and sacrifices of raising children. Childbearing is no longer the nearly foregone conclusion that it once was. People whose careers demand long stints in school and training (and their associated costs) often will delay getting married or entering into stable relationships. And, at present, the lack of confidence in national economies discourages people from taking on additional financial responsibilities. For many people, finding a secure job with adequate pay has become an arduous task.

Very low fertility rates are well-documented in many countries in Europe and East Asia, and the trend is becoming more widespread in developing countries. Brazil, Chile, Costa Rica, Cuba, Iran, Thailand, and Turkey are examples of developing countries where women average 2.0 children or less.

From Pyramid to Pillar in Thailand

Thailand has undergone the pyramid-to-pillar transition. In 1970, Thai women averaged 5.5 children each, down from around six in 1950. Click on the graphic and look at the 1970 pyramid: The very broad-base is the result of a high fertility rate. In 1970, there were 7.5 times more births than deaths. But following a national campaign in Thailand to slow population growth, women averaged 2.1 children by 1990. Click on the radio button for 1990 and you'll see that the effect of this campaign was quite dramatic, to say the least. Notice how all three of the youngest age groups (0 to 14) are smaller than the one for ages 15 to 19. A significant benchmark in a country's population change is when the youngest age group (0 to 4) becomes smaller than the one just above for ages 5 to 9. In Thailand, this change occurred around 1980.

Now click the radio button for 2010. By 2010, women in Thailand were averaging 1.6 children, well below the replacement level of about 2.1 children needed to maintain population size in the long run. And, there were only 1.6 births annually for each death, not 7.5 as in 1970. In 1970, 44 percent of the population was 14 or younger, but this proportion shrunk to only 21 percent in 2010. At the other end, people ages 65 and older represented 3 percent of the population in 1970 but tripled to 9 percent by 2010.

Thailand's 2010 pillar shows that slow population growth and even population decline are inevitable as each new group of births continues to dwindle. In these cases, the number of potential parents decreases because childbearing has become far more optional than in the past. In addition, the proportion of the elderly will continue to rise, placing increased pressure on retirement and health care systems.

No Turning Back

At some point, the trend from pyramid to pillar becomes virtually irreversible. In Germany, for example, the average number of children per woman fell below 2.1 in 1970, over 40 years ago. The birth rate continued to fall, dropping to 1.2 children in 1994 and now stands at 1.36. These remarkable results are shown in the pyramid below for Germany—sort of a pyramid! The youngest age group (0 to 4) is slightly less than half that of the group with the most people (45 to 49).

Population of Germany by Age and Sex, July 1, 2011


Source: United Nations Demographic Yearbook 2011.

Even a modest increase in the birth rate would make little difference in births in future years—there are simply too few young people coming up the age ladder. This same situation is common throughout Europe and is evident in Japan, South Korea, and Taiwan.

Are Pillars the New Demographic Reality?

Is this the new demographic reality? For many wealthier, industrialized countries, the answer is yes. When living standards rise and there are many competing alternatives to raising families, it seems that fertility often falls to unforeseen low levels. Demographers are watching for the pyramid-to-pillar transition for other countries too, especially for developing countries.

Carl Haub is a senior demographer at the Population Reference Bureau.


  1. As defined by the United Nations, the developing countries are those in Africa, Asia (less Japan), Latin America/Caribbean, and Oceania (less Australia and New Zealand). The balance of the world's regions and countries are classified as developed.
  2. The birth rate measure used here is the total fertility rate, or the average number of children women would bear if the rate of childbearing of a particular year were to remain constant.