The uptrend in the S&P 500 stalled out leading into May, as the widely watched index was down more than 3% over the last month and down over 5% in May as of Wednesday. The pullback in the market coincided with increasing concerns over a slowdown in global economic growth, a re-flaring of the European sovereign debt crisis, and jitters about another summer sell-off. Make no mistake, many traders and investors may be eying the exits, as the old adage "sell in May, and go away" has proven prescient in recent years.