You make a great point, and the title of the article is misleading at best, really just plain wrong IMHO. But the title also doesn't state he isn't invested in the stock market, only that he doesn't own any individual company stock.
Personally, I think this version is the most fair way for politicians. On one hand, any investment for them gives them incentive to put market health (money) over their constituents. On the other hand, investing in a 401k or mutual fund is something everyone should do, how else will you afford retirement?
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