Nothing is simple anymore.
Not even investing in index funds. Time was, you could park your money in an index fund, sit back, and not worry too much about it. The rest mirror everything from the broad Wilshire 5000 Index, which tracks the entire U.S. stock market, to the volatile Morgan Stanley Capital International Emerging Markets Index, which tracks the markets of developing countries. The result is that many index-fund investors now have to approach their decisions with a lot more sophistication than they did even a short time ago. The concept is much broader.