Ethnicity and IQ heterogeneity: I was curious about IQ diversity among American ethnic groups. Selecting GSS groups with at least 100 respondents, I calculated the coefficient of variation, a normalized measure of dispersion, for Wordsum scores. Here are the numbers:
Coefficient of variation
Puerto Rican .491
Racially mixed groups are the most IQ-diverse, and Scandinavians and Jews are the most homogeneous (many of those Russians are Jews).
With Mexican Americans especially, we should avoid talking about them like they are a monolithic group.