The Academic Origins of China's One Child Policy

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In our latest Freakonomics Radio podcast, “Misadventures in Baby-Making,” we describe an academic paper by a Dutch mathematics professor that might have been one of the inspirations of the controversial One Child Policy in China.

Here’s the story: in the early 1970s, Geert Jan Olsder co-authored the paper “Population Planning; a Distributed Time Optimal Control Problem.” He saw population as a mathematical constraint problem, where an optimal birth rate could be found:

“Given a certain initial age profile the population must be “steered” as quickly as possible to another, prescribed, final age profile by means of a suitable chosen birth rate.”

The model considered the natural birth rate and mortality rate, an economic constraint, and time. And like any good empirical scientist, Olsder makes this warning in his paper:

“This paper is not concerned with the social and political problems involved in establishing the best mechanism for a program of population management….The optimal birth rate may unbalance the age distribution during the time interval concerned, which could give rise to economic and social problems.”

He meets Song Jian, a visitor from China with a Ph.D. in engineering from Moscow University. According to Olsder, they went out for beers and talked about population planning. Olsder thought nothing of it.

Song was a ballistics missiles specialist, but by the end of the 1980s he had established a theory of population control in Chinese political and science circles. Susan Greenhalgh, an expert on the One Child Policy who served 10 years at the Population Council, notes in her book that Song formed his theory largely based on ideas from the Club of Rome publication The Limits of Growth — a 1972 Malthusian work that hinted at catastrophe if resources and population were not balanced. It applied straight forward equations to economic outlooks without data, an approach that economists have since dismissed.

Armed with The Limits of Growth, along with computations and models that called for drastic policy change, Song took his hard science approach to powerful party leaders in Beijing. Here’s Song’s bio from the China Daily website:

“With his knowledge of cybernetics, Song worked out a theory of a bidirectional limit to the total fertility rate. This helped the Chinese leader to formulate the state family planning policy, particularly the “one couple, one child” policy.”

The rest is history. Three decades later, the policy has led to severe gender imbalances in some parts of China, which is also facing a potential demographic disaster due to its aging population. Ironically, China might have the opposite population problem now: too low a birth rate.

For more on Song Jian and the One Child Policy, check out Mara Hvistendahl‘s piece in Science.