NEW YORK ( TheStreet) -- To attract nervous investors, fund companies have been introducing low-volatility ETFs, which can provide protection in downturns. Recently the funds have been delivering winning results. While the S&P 500 lost 3.7% in the past month, PowerShares S&P 500 Low Volatility ( SPLV) gained 0.2%. Over the past 12 months, the PowerShares fund returned 11.7%, outdoing the benchmark by 7 percentage points.Other funds that provided some cushioning in recent downturns include Russell 1000 Low Volatility ( LVOL), Russell 2000 Low Volatility ( SLVY), and iShares MSCI Emerging Markets Minimum Volatility ( EEMV). If the markets remain jumpy this summer, as many analysts expect, the low-volatility funds could continue outpacing the benchmarks. Most of the low-volatility funds are less than a year old, so it is too soon to know if they will have staying power. But academic research suggests that over long periods, low-volatility stocks have matched or outdone the overall market while taking less risk. Why can low-volatility strategies perform so well? Some researchers say that low-volatility stocks tend to be boring issues such as utilities and consumer staples, which report steady earnings. Because they suffer little damage in downturns, the stocks have a big advantage in choppy markets. In contrast, high-volatility stocks tend to be in sectors like technology, which often attract notice from investors. The glamorous companies can be overpriced in bull markets -- and suffer big losses in downturns. Investors who are attracted to the low-volatility strategies should keep in mind that many of the funds can be concentrated in a few sectors. The PowerShares fund has 60% of its assets in utilities and defensive consumer names. In contrast, the S&P 500 only has 15% in the two sectors. PowerShares only has 1.8% of assets in technology, compared to 18% for the S&P 500. The fund companies use different methods to select low-volatility stocks. The PowerShares fund picks the 100 stocks in the S&P 500 that recorded the smallest price swings in the past year. Each stock is weighted according to its volatility. So the least volatile stocks account for the greatest weighting. The biggest holding is Southern Co. ( SO), a regulated power producer. Other top holdings include such stable consumer stocks as Coca-Cola ( KO) and Kimberly-Clark ( KMB), maker of Kleenex tissue.