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.