Fertility rates are inversely proportional to intelligence. That is, the more intelligent you and your spouse are, the fewer children you are likely to have. Rudimentary statistics tells you that the average intelligence of the entire population will fall.
Now, compounding this are two additional factors:
1. One of the balances to the fertility rate problems has been the
Darwinian one -- low IQ is not a survival characteristic. That is, peoples with
low IQ tend to have lower life expectancies. Therefore they reproduced at lower
rates. Modern science and technology has intervened to reduce the effects of
life-threatening disease -- from malaria to Ebola.
2. As Charles Murray pointed out in Coming Apart, the tendencies
for like to marry like are increasing. Since a child’s IQ is highly correlated
to that of his parents, this means that instead of reverting to the mean, IQ is
becoming more bi-modal – that is, greater concentrations at high levels (low
fertility) and low levels (high
fertility).
All of this
suggests strongly that we should expect the decline of the last 50 years to
continue. Not a particularly positive trend in light of the fact that technology
is also rapidly eliminating the sorts of jobs that people with lower
intelligence can do.