From Turkey’s PISA 2015 National Report:
In 2015, Richard Lynn and coauthors did one of their standard national IQ analyses on Turkey (based on the results of PISA 2012).
There are seven points of interest in the results. First, the total PISA scores adopted as IQs were significantly positively correlated with per capita income (r = .81), higher educational graduation rate (r = .63) and with educational achievement measured by the YGS examination (r = .87), and significantly negatively correlated with total fertility rate (r = −.89), the infant mortality rate (r = −.80) and the percentage of Kurds (r = −.87).
If Europe’s (and Russia’s) problems with low-IQ, high-fertility minorities with a chip on their shoulder seem bad, Turkey’s are arguably far worse.