The study below is one I have shown a few times in the past. It suggests that when SPY closes strong (in the top 10% of its range) but still only manages a small gain on the day, that the next day has a downside tendency. Here is the stats table.
As you can see the numbers imply a bit of a bearish inclination. It appears that when the market needs to expend a fair amount of energy just to squeak out a small gain, that its lack of momentum is often followed by a swing back in the opposite direction the next day.
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