Supporters of IQ testing have been quick to point to correlations
between IQ and job performance as evidence of test validity. A closer
look at the data and results, however, suggests a rather murkier
Hundreds of studies prior to the 1970s reported low and/or
inconsistent correlations between IQ and job performance.
The claim that the IQ-job performance correlation increases with job
complexity is not born out in more recent studies.
This supports the claim that the topic has been widely-studied, if that's what this question is trying to get at.