I posted earlier about this observation here. As you can see on the chart below SPY and EEM (emerging markets) have been closely correlated except since the beginning of this year. Most of the time the correlation was close to 1.0. This year the correlation turned negative for a longer period of time. Something has to give. We will find out in a month or two.
I mainly focus on the SPDR S&P 500 (SPY). It follows the movement of the top 500 stocks and therefore it gives a good indication about the Market's health. SPY moved up quite a bit since mid November and it's about time to take a break. I am not talking about a Market Crash just a healthy correction. Indicators I have been using showing that the momentum is slowing down and just the past week we also had a couple of days when noticaeble selling took place with higher volume. Of course the Market won't go straight down and reverse right away. There will be some up days so called oversold bounces. I also closely watch other Markets such as Emerging Markets (EEM) and European Markets (EFA) and I see the same correction is taking places in fact started earlier. International Markets a closely correlated so it's a good idea to keep an eye on them.