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Population Growth to Cease in 2075, Experts Say - 2001-08-01

Researchers say world population growth may cease by 2075. A new study appearing in the journal Nature says the number of people in the world, which has tripled in the last 75 years, will not even double in the next 75 and is likely to decline after that.

The United Nations says world population reached six billion last October. Now, a new projection by the International Institute for Applied Systems Analysis (IIASA) in Vienna sees a high probability that population growth will stop at just under nine billion in 2075. Then it predicts a decline in the last quarter of the century to less than 8.5 billion.

IIASA demographer Wolfgang Lutz led the study with U.S. and Dutch scientists. "The main reason for this end of population growth is that fertility in many populations around the world has already reached levels below replacement level of two surviving children per woman," Mr. Lutz says. "It means in the long run if you are below this level, the population is going the shrink."

The IIASA projection considers thousands of different scenarios for future world population based on current trends and the assumptions of many demographers. It assigns a probability to each range of possibilities.

The nine billion limit it foresees is its middle estimate and is more than one billion people lower than the middle estimate of its last study four years ago. Mr. Lutz says this is because fertility rates have dropped more rapidly than anticipated, coupled with higher death rates from AIDS.

"AIDS in Africa essentially, but also in India and other parts of the world, has been a new factor," Mr. Lutz says. "In Africa it has been a significant factor, decreasing life expectancy in some countries below 40 years. That means that with high mortality rates, populations are going to grow much less."

The median U.N. population projections are identical with IIASA's through 2045. But instead of falling, the U.N. numbers remain level based on different assumptions about fertility.

Nevertheless, both estimates assume an end to world population growth in this century at roughly 9-10 billion. Wolfgang Lutz and his U.S. and Dutch colleagues call this welcome news for efforts toward sustainable development.

One family planning expert agrees but only if demand for resources also peaks. The expert is physician Victoria Wells of the Center for Development and Population Activities in Washington, which uses U.S. aid to provide family planning services around the world. "When we're looking at the world as a source of finite resources, individual consumption makes a huge impact on those resources," Ms. Wells explains. "If we inflate our consuming as we diminish our numbers, we're not going to achieve a more long-lasting world."

Another expert worries that the new IIASA projection might cause complacency among international aid donors. Robert Engelman, head of population studies at the private Washington group Population Action International, fears it could trigger a drop in the very family planning assistance that would help the forecast become reality. "If people in Africa are going to have the kind of levels of fertility that we see now in Europe," Mr. Engelman says, "it's going to take a global effort to provide reproductive health care and family planning to the billions of people in the world who don't really have good access to it."

The IIASA population model raises another serious issue. It predicts major growth in the numbers of elderly. Wolfgang Lutz says the proportion of people over age 60 will more than triple by 2100, from 10 to 34 percent. "This will really be the major demographic challenge of this century to cope with this massive population aging."

Mr. Lutz says it will become very expensive for countries to offer old age security programs with a dwindling proportion of younger wage earners to pay for them.