"People would be a lot more skeptical if they understood that there is an incredible amount of chance in the results that you observe for active managers. So the distribution of outcomes is enormously wide - but that's exactly what you'd expect by chance with lots of active managers who hold imperfectly diversified portfolios. The really good portfolios contain a lot of really lucky picks, and the really bad portfolios contain a lot of really unlucky picks as well as some really bad ones."

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Still, I figure we shouldn't' discourage fans of actively managed funds. With all their buying and selling, active investors ensure the market is reasonably efficient. That makes it possible for the rest of us to do the sensible thing, which is to index. Want to join me in this parasitic behavior? To build a well-diversified portfolio, you might stash 70 percent of your stock portfolio into a Wilshire 5000-index fund and the remaining 30 percent in an international-index fund.

— Paul Samuelson