Explanation for 80% of the current inequality

In the 9 part survey article of the issue in Slate magazine, Timothy Noah comes up with a rough estimate of the causes of our current income inequality.

• Race and gender are responsible for none of it, and single parenthood is responsible for virtually none of it.
• Immigration is responsible for 5 percent.
• The imagined uniqueness of computers as a transformative technology is responsible for none of it.
• Tax policy is responsible for 5 percent.
• The decline of organized labor is responsible for 20 percent.
• Trade is responsible for 10 percent.
• Wall Street and corporate board pay packages responsible for 30 percent.
• Various failures in our education system are responsible for 30 percent.

In summary, this article attributes 80% of the inequality to decline of organized labor, Wall Street and corporate over-compensation, and poorly educated workers. So, taxing and/or otherwise regulating Wall Street would only have a small effect on the problem--worth doing something there, but not the whole issue.