Do stereotypes contain a grain of truth? According to Satoshi Kanazawa , yes:
“Stereotypes” have a bad name, and everybody hates stereotypes. But what exactly is a stereotype?
What people call “stereotypes” are what scientists call “empirical generalizations,” and they are the foundation of scientific theory. That’s what scientists do; they make generalizations. Many stereotypes are empirical generalizations with a statistical basis and thus on average tend to be true. If they are not true, they wouldn’t be stereotypes.
But how accurate are they, anyways? In a review of the literature, Jussim, et al. (2009) found that stereotypes tend to be highly accurate, especially when judged in terms of the standards adopted in the behavioral sciences:
Table 4 compares the frequency with which social psychological research produces effects exceeding correlations of r = .30 and r = .50, with the frequency with which the correlations reflecting the extent to which people’s stereotypes correspond to criteria exceed r = .30 and r = .50. Only 24% of social psychological effects exceed correlations of r = .30 and only 5% exceed r = .50. In contrast, all 18 of the aggregate/consensual stereotype accuracy correlations shown in Table 1 and Table 2 exceed r = .30, and all but two exceed r =.50. Furthermore, nine of eleven personal stereotype accuracy correlations exceeded r = .30, and four of eleven exceed r = .50.
 Kanazawa, 2008. All stereotypes are true, except… I: What are stereotypes? Psychology Today, April 24. http://www.psychologytoday.com/blog/the-scientific-fundamentalist/200804/all-stereotypes-are-true-except-i-what-are-stereotypes
 Jussim, et al., 2009. The Unbearable Accuracy of Stereotypes