Looking at a 3 year weekly chart of the SPY (S&P 500 SPDRs, Expense Ratio 0.09%), we can see that it recently moved below its 3 yr. trend-line support.
Over the long term, we notice that most pullbacks found support at its 20 week moving average. When it broke the trend-line and 20 week average, which happened on three occasions, it found support at its 50 week moving average.
Currently it is below the trend-line, which sits at 212.50. The 20wk. support is at 207.04 and the 50wk. support is at 200.79. You can notice on the chart above that its RSI has been declining since June of 2014, indicating internal weakness.
In other words, not everybody is enjoying the upside trend. Its MACD has also began to cross below the signal line. We see the combination of these signals as cautionary indicators.
The SPY needs to cross back above the trend-line support of 212.50, to regain its upside bias, until then downside bias will continue and we need to look for the 20 and 50 week levels for support. A breakdown of those levels may indicate a more meaningful pullback or correction.