Tao, I have the may 2015 high as 2134.72 and the January 2016 low as 1812.29 that gives me a 15% correction from the May high to the Jan low. this most recent Jan 20 low makes a double bottom with the Oct 2014 low. I'm guessing that this is it for now. The next stop down would be 20% at ~1707. I fully agree we were due for a correction. Possible we could move as low as 1700 , but if we do, I wouldn't expect it until later this year. I think the bottom is in for now wiyth this recent 15% correction. Once you get past 20%, in my opinion, you have gone past what is reasonable to call a correction, and one expects a reason other than stocks having just got too far ahead of the economy and therefore needing to correct. Of course there is usually a trigger event, China in the present case. As stocks get toppy, as after a seven year bull market, we start to get abit anxious and become more cautious about buying, then all it takes is a mild trigger event to start the correction. (Is my calculation off somewhere?)