NEW YORK (TheStreet) -- As summer comes to an end, trading volume remains low and uncertainty over central bank policy weighs on investors' minds. The low volume means price swings are more volatile than usual. With less of a fight between bulls and bears, markets are more easily swayed by strong conviction from one side or the other.U.S. equity markets appeared to be overbought for the past few weeks, as prices trended sideways. A correction finally occurred last week when fears of Federal Reserve policy tightening overtook trader sentiment. The chart below is of SPDR S&P 500 ( SPY). The equity index traded in a tight range for most of July and August. The index surpassed the 1,700 level for a few days, but lacked a catalyst to push it above that level.