In her office, among carvings, prints, and keepsakes from around Africa and Asia, social demographer Amy Ong Tsui stashes a wooden bowl brimming with an international collection of birth control methods -- cycle beads, condom packs, a female condom, pill packs, emergency contraception and more from clinics around the world.
It's a fitting collection for someone who's studied reproductive health and population for four decades.
"I'm interested in some of the behaviors that drive human population change, and reproduction is the biggest driver of population change," says Tsui, 62, director of The Bill and Melinda Gates Institute for Population and Reproductive Health, and professor of population and family health sciences at the Johns Hopkins Bloomberg School of Public Health in Baltimore, Maryland.
Among the areas that have recently intrigued Tsui is how patterns of childbearing -- number and timing of births -- relate to health. "There's a widely held belief in my field that child spacing is healthy for child and mother, but there is surprisingly thin evidence to back that up," she says.
At Hopkins, she primarily teaches family planning and reproductive health, and advises students. With the Institute, she collaborates with universities in Egypt, Ethiopia, Ghana, Malawi, Nigeria, and Uganda that have their own population and reproductive health centers. The Institute strengthens their research and teaching capacity so that they can compete on an international or regional peer-review basis. Her role is advisory, helping to design studies, analyzing data, and improving the quality of the data.
Tsui's international outlook was fostered at an early age. Her father, a native of China, was finishing his Ph.D. in the United States when Tsui was born -- about the time of the revolution in China; he then took a position with the Food and Agriculture Organization of the United Nations that brought the family to Bangladesh, and later Thailand. Tsui returned to the United States to finish high school and began her undergraduate degree in Minnesota; she finished her Bachelor's and then her Master's degree in Hawaii, where her family had settled.
For her Ph.D. at the University of Chicago, she worked with advisor Donald Bogue to examine the role of contraception in fertility, and how increased access to contraception in developing nations could impact population growth.
At that time, in the early 1970s, the United Nations and the World Bank were predicting future population numbers would skyrocket. Paul Ehrlich's book, The Population Bomb, had just come out (1968), and concerns about population in China were running high. "Population growth was the celebrity issue -- just like HIV and climate change have become more recent celebrity issues in science," Tsui recalls. "There was this concern that the developing world population was just going to explode."
She and Bogue coauthored an article called "Zero World Population Growth?" in The Public Interest (1979) that predicted fertility to drop faster because of contraceptive methods. "We projected world population to be 9 billion in 2050," she says. Their calculations were criticized for being overly optimistic.
But time would prove "we were dead on," Tsui says. In 2010, the UN projected the world's population to hit 9 billion by 2050 and predicted it could hit 10 billion by 2100. This year, demographers expect world population to reach 7 billion on October 31.
A self-described workaholic, Tsui likes the international travel aspect of her job. Sri Lanka ranks among her favorite destinations; she visited the country in the early 1990s to conduct a study on noncontraceptive methods (such as timing, or rhythm). "It's an island nation that's often forgotten, but one of the most progressive cultures -- they gave women the right to vote early on, and had good reproductive health indicators," says Tsui, who says the island reminded her of growing up in Thailand. "I was very comfortable there because of the nature of the religious atmosphere ... and it's very beautiful."
As a social demographer, Tsui has noticed a shift in her field in the last few decades. "There's still a vibrant population research field, but it's become more diverse," she says — new areas include aging, family demography, migration, health disparities, and pregnancy. She's also seen reproductive health change around the world. Back in the 1970s, there were few available family planning methods. "Now, we have a lot of methods," Tsui says. "The diffusion has been remarkable in the last 40 years."