There is now plenty of evidence of variability in national average IQs and equally strong evidence that the differences concerned matter a lot. To put it bluntly, low IQ nations tend to be hellholes and high IQ nations are prosperous and comfortable.
An odd exception to that was China, with a very high average IQ but also high levels of poverty. Recently, however, we have seen that with the yoke of communism partially removed from them, the Chinese have been going ahead economically in leaps and bounds -- and they will undoubledly soon arrive at the level of prosperity that their average IQ would indicate. China's recent advance is in fact an excellent validation of IQ theory. Just giving them the opportunity to realize their potential produced amazing successes. It is exactly what IQ theory would predict for a high IQ nation.
In all countries, however, economic advance is driven by a small minority. Most people are "wage slaves", not entrepreneurs. So among IQ researchers there has been a proposal that it might be more enlightening to look not at the average guy but rather at the top people in his nation's population. We should take (say) the top 5% (as measured by IQ score) of any population and look at THEIR average IQ rather than the average IQ in that nation as a whole. The average IQ of the "smart fraction" in a population might give us even better predictive power about that nation than the average IQ of that nation as a whole does.
Recently, some research has been done which tests that theory. They did not use IQ scores as such but estimated IQ from measures of educational attainment. Educational attainment and IQ are highly correlated. The journal abstract is below:
The impact of smart fractions, cognitive ability of politicians and average competence of peoples on social development
By Heiner Rindermann, Michael Sailer and James Thompson
Smart fraction theory supposes that gifted and talented persons are especially relevant for societal development. Using results for the 95th percentile from TIMSS 1995- 2007, PISA 2000-2006 and PIRLS 2001-2006 we calculated an ability sum value (N=90 countries) for the upper level group (equivalent to a within country IQ-threshold of 125 or a student assessment score of 667) and compared its influence with the mean ability and the 5th percentile ability on wealth (GDP), patent rates, Nobel Prizes, numbers of scientists, political variables (government effectiveness, democracy, rule of law, political liberty), HIV, AIDS and homicide.
Additionally, using information on school and professional education, we estimated the cognitive competence of political leaders in N=90 countries.
Results of correlations, regression and path analyses generally show a larger impact of the smart fractions’ ability on positively valued outcomes than of the mean result or the 5th percentile fraction. The influence of the 5th percentile fraction on HIV, AIDS and homicide, however, was stronger.
The intelligence of politicians was less important, a longitudinal crosslagged analysis could show a positive influence on the cognitive development of nations.
So the results supported the theory. How smart a nation's smarties were told us even more than average IQ did. Note the very large number of variables that were successfully predicted by the study. How smart your nation's smarties are is very important indeed.
Note also that how dumb the dummies were (the BOTTOM 5%) also strongly predicted a few things: The incidence of HIV, AIDS and homicide! To put it very bluntly, real dummies are murderous and will stick their dicks in anything.
Steve Sailer has a much more detailed discussion of the paper but misses the point that IQ in even the Jewish population of Israel (not counting the Arabs and the illegal immigrants) is bimodal. Most Israeli Jews are of Middle Eastern origin and hence not too bright. It is the minority of Israeli Jews who are of European origin (Ashkenazim) who account for Israel's advances. To really understand Israel, you need to treat the Ashkenazim as a separate population in its own right. They are in their own way a good example of how important the "smart fraction" is.