There are three main reasons why the correlation between national IQ and GDP per capita is only around r=0.7, instead of r=0.9.
Oil/resource windfalls: Saudi Arabia would otherwise be about as prosperous as Yemen.
The legacy of Communism: Central planning and especially the lunacy that is Maoism are far less effective than free markets.
The legacy of Malthusianism: This is the most subtle factor, but it used to be very important. Countries like China, Japan, and to a lesser extent India used to be stuck in a high-level equilibrium trap; quite intelligent and productive, but unable to accumulate capital surpluses due to almost everyone being at the limits of subsistence.
This was not the case with relatively land-rich Latin America, where escaping from the Malthusian trap was easier. As a result, the degree of human capital there has long correlated much better with the region’s wealth. (Argentina even had a resource windfall effect around a century ago).
But all these factors will diminish in the coming decades!
Practically everyone outside Sub-Saharan Africa has more or less escaped the Malthusian trap.
Communist regimes have nearly all collapsed, leaving just a few relics like Cuba and Best Korea as monuments to failure. Moreover, over the long term, we can expect institutions everywhere to get better, as different countries adopt established best practices – occasional backsliding as with Venezuela regardless.
The impact of resource windfalls – apart from a few exceptions (e.g. Botswana – diamonds), we’re speaking about oil – will likewise decline. Technology has conquered Hubbert’s peak from the supply side, and soon enough, electric batteries are going to cut in from the demand side.
Even today, it is presumably not an accident that the countries with the most developed automation in manufacturing – Germany, Switzerland, (Northern) Italy, Japan, South Korea, parts of the United States, and increasingly, China – are those where the core populations have 100-105 range average IQs.
The coming automation of more and more sectors of the economy, including services, will impact disproportionately on low IQ jobs, so the impact on economic performance of average IQs – and especially smart fractions – should if anything increase even further.
The one thing that could throw a wrench into this – sort of – is if countries were to begin randomly adopting large-scale intelligence augmentation at highly differential rates (e.g. via CRISPR + genomics of IQ). But it isn’t likely to be random. It will almost certainly be the richest and least superstitious/obscurantist countries that will adopt these technologies first, and both of those factors are already highly correlated with IQ.