Are recent down days in the market a sign the rally is losing steam? Since the Mar. 9 low of the Standard & Poor's 500-stock index, there's been a spike in so-called short interest, a sign investors are betting stocks are due for a fall. The short interest ratio—the number of shares borrowed and sold short, divided by a stock's average daily trading volume—for S&P 500 stocks is currently 3.0, up from a Feb. 27 low of 2.3. Typically, the higher the ratio, the more gloomy the outlook, since a larger percentage of shares that are actively traded has been shorted. Consumer discretionary companies, including those in the auto and manufacturing industries, have an average ratio of 3.9 now, the highest among all sectors. Five S&P 500 companies have ratios of more than 10.0: Harley-Davidson ( (HOG)
), CenturyTel ( (CTL)
), Fastenal ( (FAST)
), Quest Diagnostics ( (DGX)
), and New York Times Co. ( (NYT)
) On the flip side, battered financials boast some of the lowest ratios, with Bank of America ( (BAC)
) and Regions Financial ( (RF)
) boasting ratios at less than 0.5.