Dr. Joseph Chamie knows the world like the back of his hand.

As director of the United Nations’ Population Division, he's been examining demographic numbers from around the world for 28 years. The Population Division is separate from the United Nations Population Fund, which has been criticized by watchdog groups for “ideological” use of data.

Prior to his work at the United Nations, Chamie and his wife served in the Peace Corps in India. He spoke recently with Register staff writer Tim Drake from his office in New York.

How did you get started studying population?

I was born in the Detroit area. My father was an autoworker. He and my mother were immigrants from Lebanon. I received my undergraduate degree at the University of Michigan. President John F. Kennedy's announcement of the Peace Corps inspired me to join. I served in India between1967-69. When I came back, I attended graduate school and graduated with a Ph.D. in sociology, specializing in population studies.

In the 1950s and ’60s, the conventional wisdom was that fertility had to do with religion. U.S. behavior showed that the biggest population differential showed Catholics at the top and Jews at the bottom, but that data was being confounded by immigration.

I did research for my thesis in Lebanon. Lebanon is home to 16 religious groups; therefore, it provided an ideal laboratory to test what impact religious upbringing would have on fertility behavior. In Lebanon, I could control for immigration. What I discovered was that the differences in fertility are transitory. As each group passes through modernity, it follows a pattern of low fertility.

I subsequently published my research as a book, and after finishing a post doctorate, I began working for the U.N. For the first five years, I worked in Jordan and Beirut. In 1981, I came to New York and worked my way up. I became director in 1993.

Did you find that religion plays a part in population?

When I began studying this in the early 1970s, there was a myth that there was a religious differential and that Catholics had more children. We dispelled that myth. Now we're dispelling the myth that Muslim countries are having more children. The Islamic Republic of Iran has a population rate of 2%. In Tehran, it is below that.

Why are numbers so important?

Demographics have political dimensions. Around the world, issues of demographics are coming up. Ever since Adam and Eve, the tribe has mattered. In a democracy, demography counts. If you had gone with the coalition to Iraq, you would have seen political reorganization based on demography. Demography also has a bearing in the U.S. elections. Once President Lincoln gave votes to blacks, it had an immediate effect. After women got the vote, politicians started talking about women's issues. Today, we're seeing that happen with Hispanics. Those groups that are larger get more attention.

Why are people having fewer children?

There are many reasons for the decline: urbanization, education, cohabitation, contraception, abortion and divorce. When the death rates come down, you don't need a large population in order for people to survive. Children have a role on the farm, but in the city, they don't. Urban life brings smaller quarters. We've moved away from the family being a safety net to the government being the safety net.

Modern birth control has also had a dramatic impact. Contraceptive prevalence has doubled between the 1950s and today. Today, 61% of all women are using some method of contraception. In Brazil, we estimate that 40% of married women have been sterilized by choice.

We also know from studies that female education has brought down fertility. Women stay in school longer, thereby postponing marriage and the first birth.

What are countries doing to try to combat low fertility?

Some countries are trying to facilitate the dual-career couple to have children. France, Italy, Japan, Singapore, Korea and Russia are enacting child-friendly policies such as giving priority for housing to couples with children. In France and Italy, the government has tried financial incentives. Singapore is trying to make childbearing more compatible with modern-day employment. In England and Australia, they are using tax breaks. A treasurer in Australia has developed the motto: “Have three children. One for mom, one for dad and one for the country.”

Can such policies make a difference?

It will make some difference, but not enough to raise the birth rate up to two (children per couple). There are too many forces operating on men and women.

Tim Drake writes from St. Cloud, Minnesota.