I think you would be correct in saying that. Moreover, to use Don's argument, there are probably more variables with higher income earners. Statistically, it would be easier to see a difference of $20,000 or $30,000 if one of them earns about $100,000 and the other $70,000, even if both are working. So I would say that it is indeed the case. Your assessment is quite accurate.
On November 23rd, 2006. See this statement in context.