You have to be very careful with this stuff. The hucksters are getting very cagey.
If you go back to William Sharpe's 1993 paper,
The Arithmetic of Active Investing, in three pages he makes it crystal clear why the average of all active managers delivers the market average, before costs, and is beaten by passive managers whose cost is less. Sharpe won his Nobel prize a couple of years prior and has a very good command of arithmetic.
The important thing to understand, though, is that Sharpe's average is the market average of the market where the active managers are working. The arithmetic does not work if the measuring stick, the market average, is measuring something different than where the active managers are working.
So what is happening is that the active managers are leaving their stated styles in order to pursue gains that will make them look good against the measuring stick for their nominal style. Sometimes this works, sometimes it does not. It's just stock picking after all. A few weeks ago I read an article that advised active managers to do exactly this -- abandon their style constraints and seek opportunities in styles outside their stated style.
So, nothing has really changed except that the hucksters are getting smarter and smarter about how to fudge their results to look like they are winning. The result, though, is that we as investors can no longer be sure that when we buy a particular style, like large cap US stocks, that the fund manager will actually be sticking to the style. With the decline of the dollar and consequent apparent rise in international stocks, they may be buying in Europe in order to look good against their (now somewhat irrelevant) benchmark.
