US stocks continue to impress in absolute and relative terms in 2013. For the year so far (through July 9), no other major asset class even comes close. Based on a proxy ETF, the total return for US equities in 2013 is nearly 17%. Using history as a guide, that’s the equivalent of earning nearly twice the long-run performance in six months. Enjoy it while it lasts. At the opposite end of the spectrum: emerging market stocks, which are deeply in the red by almost 14%.