Used with permission of the National Media Museum
A study published this week in the journal Nature brings into question the prevailing wisdom about how a country’s development impacts its population growth. Previously, social scientists thought that indicators such as health, standard of living and human capital, collectively called the Human Development Index, could reliably predict negative population growth.
In the past, data showed that wealthier, better educated and healthier countries had lower fertility rates. This rate is defined as the total number of children the average woman bears through her reproductive years. For example, the US has a Development Index of about 0.9 (one being the highest) and an fertility rate of about 2 children per woman. This is the magic number where the man and woman who conceived the child are replaced. Whereas for Niger, an undeveloped African country with a Development Index of about 0.3, the fertility rate is 7 children per woman. This means that the average Nigerian couple replace themselves more than 3 times over!
However, the study authors found that once a country’s Development Index surpassed 0.9, that the fertility rate begins to increase. For example, the US fertility rate is 0.25 higher than it was in 1976 . This increase is true for over 20 other well-developed countries that have passed the 0.9 mark. For countries currently experiencing population decline this may be of some comfort, as a decline is associated with deflation and the collapse of social welfare systems.
For more on this study, check out Andy Revkin’s New York Times blog post which explores some of the environmental implications in regards to world population growth. In addition, here is a neat Java Script application developed by Loren Cobb of the University of Colorado, which helps visualize population growth based on different parameters–like fertility rates.
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