A gap, when dealing with candlesticks, is formed when the previous close price is different than the next open price. It implies heavy position rollings by big shots (istitutionals, etc) and makes for greater volatility. This behavior is common among illiquid instruments and during nasty times. You can see a couple on GOOG, AMZN, AAPL and others. Now you see it in SPDR. These, are the most liquid assets in the world. This period though, is not nasty. Valuations are going high and political scenarios are less grimey than thought (EU populism, low volatility, stuff like this). This given, gaps that big in the SPY are very not common, thus I am calling for a $260 correction.