Be careful of a bear trap here. Remember, DIA, SPY and QQQQ all go ex dividend tomorrow. I suspect that some big institutions have gone big time long yesterday and today to collect some quick and easy dividend cash. After 7 days of broad selling in these popular index funds, it makes sense they are overdue for a bounce anyway. Short positions held today will be charged a dividend payment. I expect tomorrow the institutional longs will sell and the would-be institutional shorts will open new short positions. Just something to be aware of and be cautious about.
It is very unlikely that big institutions would do that, if "big instituations" mean those pension funds like CalPERS, or big mutual funds. Now, if you include hedge funds, then I'm not sure. They pretty much can do whatever they want to.
It is the brokerage houses like Merrill Lynch, Goldman Sachs, etc., that play this kind of game. The dividend yield on DIA is 3.1%, it is 1.7% for SPY, and .3% for QQQQ. When these giant indexes go up, all of the member stocks must be purchased. The multiple other indexes work the same way. If Merrill was short 1M shares of DIA, for example, they might have covered to avoid paying out the dividend. Alternatively, they might just have purchased 1M shares to collect a quick dividend payment. These brokerages have a leg up on retail investors; I believe they will be pushing down the markets tomorrow by shorting and just plain selling in Europe or here before U.S. retail trading begins.
A note on Technicals: Look at the charts for DIA, SPY, QQQQ, as well as COH; today's action brought the prices of all 4 right to the downward peak trendline (lower highs) of the last 4 - 6 weeks. I anticipate a down day tomorrow and a continuation for the next week and a half as the angst builds over the upcoming FOMC meeting 6/26-27. Today would have been a good day to sell some shares IMO; I did.