Not so much, I think. If you were correct, then why does the gap fluctuate so much from one year to the next? The answer is the economy. When the economy goes down the shitter, the bottom half suffers the most. Those with less education tend to be in the bottom half. Immigrants and ghetto dwellers have much less education.
Yes, I think so. But I don't think it's because "the bottom half suffers most". I think it's because the bottom swells with newfound sufferers, pulling the medians in each category closer to zero where the ratios can swing wildly.
You answered your own question. With economic fluctuations the ability of the diligent and constructive to increase their net worth also varies.
The fundamental character attributes I cited are bedrock fundamentals for wealth accumulation, and like it or not, are often starkly different in a juxtapostion of the groups cited.