One thing that has perplexed me for the entire year as the US market rally is the poor performance of all the other markets in the world. Emerging markets for example, is down almost 16.5% YTD, vs the still positive 11% in the S&P 500. This same trend is also found in a number of other assets such as gold, commodities, etc. The US stock market is almost the only asset class still positive for the year.
Say what you will about decoupling but there's few explanations I can reasonably accept that would explain a +11 and -16% gap.
As Bespoke.com showed in this chart, the rest of the world is vastly oversold.