Without knowing much about it, I assumed that China was bright and getting brighter, if only because bright and wealthy Chinese found a way round the One Child policy in order to have two children, thus achieving a eugenics program on the sly.
However, I have now to revise my vague surmise on the basis of some hard facts. It appear that there has been dysgenic fertility in China for both intelligence and educational attainment between the 1960s and the mid-1980s, and the decline owing to dysgenic fertility came out to .31 points per decade between 1986 and 2000.
This is not an enormous amount compared with the positive Flynn effect, if one can rely on that, but as an underlying trend it is worrying.
Mingrui Wang, John Fuerst, Jianjun Ren. Evidence of dysgenic fertility in China. Intelligence 57 (2016) 15-24.
The authors say:
The relationship between fertility, intelligence, and education was examined in China using a large sample sourced from the population-representative China Family Panel Studies (CFPS) dataset. For the 1951–1970 birth cohort, the correlation between fertility and gf was−.10. The strength of recent selection against gf in China substantially increased between the 1960s and the mid-1980s. Later (between 1986 and 2000), the speed of decline in gf due to selection stabilized at about .31 points per decade with a slightly downward trend. The total loss from 1971 to 2000 due to dysgenic fertility is estimated to be .75 points. A negative relationship between educational attainment and fertility was additionally found. Both negative relations were stronger for women.
The authors first examine the dysgenic argument:
In modern times, mortality rates have been reduced as a result of improvements in public health, nutrition, and the control of infectious diseases (Lynn, 2011). As a result, selection against deleterious mutations has been relaxed. Additionally, in many societies, individuals with lower levels of intelligence and education have begun to reproduce at higher rates than those with higher levels of these traits. Due to a reversal of selection for socially important traits such as intelligence, genes promoting these traits may decline. This phenomenon is termed dysgenics. Intelligence has been found to influence many outcomes both on the individual and societal levels.
Taking data from the China Family Panel study and the cognitive tests used in 2012 were composed of two word memorization tests and a number series test, both of which measure gf. Short term memory ability, in particular, has been found to be moderately to highly correlated with gf. However, this is hardly a broad band assessment of cognitive ability.
There is a general downward drift, though the rate of fall appears to be reducing
The authors are very cautious about their findings, making it clear in their discussion that there could be a recent increase in ability, and outlining possible confounding variables, including the urban/rural balance (moving to the cities, citizens become richer and have fewer children), iodine supplementation, selective migration to cities of brighter citizens, more participation in testing by brighter citizens, selective migration of the very brightest citizens to the outside world, and finally the actual operation of the One Child policy, which was more lax in rural areas, particularly if the first born was a girl. However, dysgenesis is even more evident in Taiwan, not affected by the One Child policy.
This is a very interesting paper, taking a cautious and detailed approach to its topic, and the discussion section is well worth reading on its own as an example of the many factors which can complicate the interpretation of these types of data.