On the Fact that (According to a 2006 Study from the Journal of Biosocial Science; Cochran, Hardy, and Harpending) Ashkenazi Jews Score Consistently Higher On the Math and Verbal Parts of Standardized IQ Tests than They Do On the Visual-Spatial Sections

This of course goes a long way in determining why this particular population ended up in the more cognitively demanding professions such as moneylending and tax-farming (from the 10th to the 18th Century) and, while, no it certainly doesn't definitively answer the chicken versus the egg dilemma of what came first (i.e., Jews being forced into certain numbers-oriented careers and having to evolve as such versus Jews being innately intelligent and choosing these occupations because of the high financial return), a stimulation for further discussion you can probably bank on.