Is modern portfolio theory (MPT) dead? Yes, according to many pundits and strategists. There have always been skeptics of modern finance, although membership in this club has risen sharply in recent years, thanks to the surge in market volatility and the steep losses posted by the major asset classes during late-2008 and early 2009. A popular argument is that multi-asset class diversification didn’t spare investors from unusually big declines, ergo, MPT failed. By that standard, the case for abandoning conventional asset pricing theory looks compelling. There’s just one problem: It’s wrong.