Much of this blog is a response to egalitarian social scientists. According to them, where people end up in life is due to external circumstances. Many of them chafe even at the idea that beliefs and values make a difference because those are too internal. You blame the victim when you argue that he is poor because he holds counterproductive attitudes.
It is obvious to anyone except an ideologue that much of our lives is determined from the inside. I often focus on evidence that racial differences can largely be explained by internal factors, and I do that because that's what many of my peers obsess on. I haven't paid much attention to social class since my peers don't. They did 75 years ago when the object of compassion was a white laborer, but he has now been turned into a privileged person. He rides triumphantly on the shoulders of others because of his skin privilege.
Class differences within races should not be ignored, however, because they are a central part of how members of society are stratified. And, as HBD-ers strongly suspect, the differences are created in significant part by the distribution of internal characteristics.
Having said that, an achievement score was calculated for white MIDUS Study participants based on the following characteristics: works hard; drives self; enjoys working hard; welcomes difficult and demanding tasks; persists where others give up; is ambitious; puts work and accomplishment before many other things; sets high standards; is a perfectionist.
Here are the mean scores listed by sex and one's current social class:
Mean achievement score (sample size = 1,187)
*significantly higher than low-status men
High- and middle-class women have signficantly higher scores than low-class men. The mean for high-status men is six-tenths of a standard deviation higher than that of low-status men--a fairly large difference.
Acording to this study, heritability for achievement is .72.
Notice how middle-class men are more driven than high-class women.