: P.S. Tell your sister that it DOESN'T MATTER if 'my stats' demonstrate EITHER the cause or the effect of inequality; either cause OR effect demonstrates that inequality exists.
The 'cause' of inequality---I'm anticipating you (or your sister now)---cannot be 'natural' inequality. Until education is available to ALL (i.e. free), we'll never know who is capable of what.
And lest we forget: only 25% of all American jobs even require any skill above a high school level (Business Week, 1 September 1997, p. 67). Which means that our 'way of living' doesn't require much skill from the population.