The year of six billion
Math of population
Problematic projections
Unsatisfied demand
Was Malthus right?
Image courtesy of the
United Nations High
for Refugees
campus crowd
Image above and crowd
scene below are
courtesy of UW-Madison
Office of News
and Public Affairs.
Photos by Jeff Miller.
Why 6 billion?

crowd of people Big baby boom
POSTED 8 OCT 1999 At the end of a record century for population growth comes another milestone. According to the United Nations, world population will reach six billion on Oct. 12. Only 12 years ago, we were five billion strong. The population of the planet has doubled in just 39 years.

Ever since Robert Thomas Malthus published his anonymous Essay on the Principle of Population in 1798, people have been disputing his contention: that population grows exponentially, but food supplies grow arithmetically. (In English, this means that the graph of population curves upward, while the graph of food supply is straight.)

Eventually, Malthus said, shortages of food would cause chaos and famine. The pronouncement was fearsome enough to earn economics this splendid moniker: the "dismal science." But it wasn't just economists who rebelled. Karl Marx also denounced Malthus.

The Bible tasked humans to "be fruitful and multiply," and could be the only commandment about which we can uniformly say, "Been there, done that." Today, India and China have as many people as were alive in 1937.

Too much good news?
The rapid growth of population largely reflects advances in controlling deaths, particularly among infants. Humans seem to carry programming to compensate for attrition during the perilous early years by making "extra" babies. It takes time to adapt after vaccines, clean water and medicines slash the infant death rate.

In general, the population booms now underway in South Asia and southern Africa follow the reduction in infant mortality. Fully 98 percent of today's population growth is taking place in developing regions, according to the Population Reference Bureau.

Eventually, however, development and birth control tend to control population growth, and population is now stabilized in the industrialized world (aside from the United States, where it's growing by 0.6 percent per year through national increase, and 0.9 percent when immigration is factored in). The average Italian woman gives birth to just 1.2 children, far below the replacement level of slightly more than two children. football game crowd Compare Italy to its former colony Ethiopia, which is growing by 2.5 percent per year. Ethiopia's population of 60 million is expected to soar to 99 million by 2025.

Needed: Elbow room
Pakistan is another area of concern. Already crowded with 146 million people, it's projected to reach between 225 and 345 million in 2050, which would shrink farmland per person to 360 square meters. Typically, says Lester Brown of the Worldwatch Institute, nations start importing food when the figure drops below 600 square meters per person (see "Breaking Out or ... " in the bibliography). Overall, population increases have tapered off slightly over the past decade as countries like Thailand and Taiwan reach the so-called "demographic transition" to smaller families. World Population: 3 Possible Futures

Still, the end is hardly in sight. According to the latest United Nations projections, the most likely scenario for population in 2050 will be around 8.9 billion, and will peak out slighly above 10 billion after 2200.

But population estimates are notoriously inexact, especially those that peer deep into the future. Even though the rate of growth is slowing, the two billion people below age 20 will be raising a lot of children over the next couple of decades.

Is it that lunch-time grumbling of the stomach? Who knows. At any rate, The Why Files is wondering: Was Malthus right? Will we eventually outgrow our food supply, or are we -- with our astounding ingenuity -- somehow immune to the laws governing other animals?

But first, how does population increase?

  The Why Files There are 1 2 3 4 5 pages in this feature.
Bibliography | Credits | Feedback | Search

©1999, University of Wisconsin, Board of Regents.