Quote from dcraig:
Regardless of stock's methodology, a distinguishing feature of the current market has been the separation of stocks into the "haves" and the "have nots". High momentum (or high relative strength) stocks have done very well and conversely the weakest stocks have fared very badly. This phenomenon has be going on for at least 12 months.
This is not just a wild assertion, but a conclusion I have reached through development of my own software for screening and some rather intensive study of this behavior. There has been a lot of money to be made in following relative strength strategies (both long and short).
Of course you need to be somewhat more sophisticated than just buying new 52 week highs, and a bit of market timing and fundamental analysis doesn't do any harm, but the overall message has been very clear.