On the S&P 500, the two levels I am watching are 1972 set on Dec 16th 2014 and 1862 set on Oct 16th 2014. Given that we have not had a 10% correction since summer of 2011, the heavy volume and level of losses for the recent leadership stocks (AMZN, NFLX, GOOG, TSLA, FB) I tend to think that the 1862 level has a very decent chance of being tested.  If it goes down to that level if would be a 13%+ correction.  So far we are about 4.6% down from the recent S&P 500 high of 2134