John Shields Aird, 85, a federal population expert who became a critic of China's one-child policy, died of multiple myeloma Oct. 9 at his home in Silver Spring.

Dr. Aird, who for nearly 30 years was the Census Bureau's resident expert on Chinese demographics, testified before Congress many times, calling the Chinese government's family planning programs highly coercive and a violation of human rights. His perspective wasn't popular with the U.S. or Chinese governments, but few could argue with his numbers.

Before China made updated census information public, Dr. Aird's job was to calculate the number of people living in the world's most populous country. He did it with high, medium and low projections and was later complimented by a Chinese official who told him that his estimates were sometimes more accurate than his own government's statements.

In retirement, he was a full-time volunteer, working with U.S. attorneys helping asylum-seeking Chinese immigrants who ran afoul of the one-child family policy. He provided expert testimony in immigration courts for 415 families.

As interested as he was in China, Dr. Aird also was involved in community activities closer to home. He was on the Montgomery County school board from 1970 to 1974, serving as both vice president and president. He was chairman of a school board commission in 1977 and 1978. For the past 14 years, he volunteered as a teacher's aide in fourth and fifth grades twice a week at Broad Acres and Highland View elementary schools.

Dr. Aird was born and raised in Detroit, where he stayed in high school an extra year so he could take classes in Latin and Greek. Drafted during his final year at Oberlin College just before the start of World War II, he served in the Army artillery as a forward observer. Conversant in several languages, he taught himself Italian while stationed in Italy so he could speak with civilians.

After the war, he graduated from Oberlin College and earned a master's degree in English literature from Harvard University in 1948. He switched fields, earning a second master's and a doctorate in sociology at the University of Michigan in 1951 and 1957.

Dr. Aird taught at the University of Michigan and Wayne State University before joining a three-man U.N. Educational, Scientific and Cultural Organization teaching team at Dacca University in East Pakistan, now Bangladesh, in the early 1950s. He also taught at Miami University in Ohio and at Vanderbilt University.

In 1957, he joined the Census Bureau's foreign manpower research office as a demographer. He focused on China from the beginning, working as chief of the China branch from 1960 to 1974, then as chief of the foreign demographic analysis division. In 1981, he was named senior research specialist on China to the director of the Census Bureau, a job he held until his retirement in 1985.

In the 1970s and 1980s, he served as the Commerce Department's representative to a group that prepared a machine-readable Chinese-American dictionary.

He was a member of the Population Association of America, the International Union for the Scientific Study of Population and the American Association for Chinese Studies. Dr. Aird published five monographs and 42 journal articles and book chapters.

He wrote two books, "Slaughter of the Innocents: Coercive Birth Control in China" (1990) and "Coercion, Deceit and the UNFPA," to be published posthumously.

Dr. Aird also served as an election judge in Montgomery in 2000, 2002 and 2004. He enjoyed classical music, reading, gardening and birding.

Survivors include his wife of 58 years, Laurel Jandy Aird of Silver Spring; three children, Steven A. Aird of Suffolk, Va., Kristen L. Mann of Columbus, Ga., and Bruce A. Aird of Lake Forest, Calif.; and eight grandchildren.