A Momentum Strategy In SPY During The Last Hour (S&P 500 Intraday Momentum)

Last Updated on June 11, 2021 by Oddmund Groette

Here is the hypothesis: if SPY rallies from the open and until the last hour, can we make money by going long one hour before the close and exit on the close?

Previously I have written about the different periods of the trading day:

This is a strategy I have traded live over the last year (just a few trades). I have tested with different thresholds, but it seems like the more SPY is up from the open (it works better from the open than from yesterday’s close), the more likely to rally the last hour. I have used a threshold of 1.25% from open to the last hour, and I get 18 fills from 2010 until the present and 13 winners. This is an average of .39% per fill, not bad for such a short holding period. Considering a total holding period of 18 hours over more than 2.5 years, a total gain of 7% must be considered extraordinary. Here is the equity curve:












There are few fills, though. Increasing the threshold to 1.5% we get 8 fills and 6 winners, and the average increases to 0.49%.

If I measure from yesterday’s close to the last hour, I don’t get such remarkable results. I’m not sure why. Does anyone have any suggestions? It’s still good, but average drops. Here are the results from yesterday’s close to last hour:

Threshold P/L #fills #wins Avg
1.25 7.41 66 40 0.11
1.5 4.89 42 23 0.12
1.75 5.53 29 19 0.19
2 4.07 21 14 0.19
2.5 3.89 12 10 0.32
3 1 4 2 0.25

To reverse it, ie. to go short if a large drop from the open, does also work (see below for explanation). For small movements, there seems to be a tendency downwards, but large drops get reversed. However, measuring from close until the last hour my results are a bit disappointing. Using from the open I get tradeable results using a threshold of about 1.5%, but 1.75% seems better (the more movement the better). Here is the equity curve for 1.75% (15 fills, 8 winners):

Why does this work? I have no idea except for the following:

  • Short covering, or
  • rebalancing in ETFs

There are a lot of traders who fade SPY. If SPY just continues higher, a lot of them might want to take a stop-loss by covering and thus needs to buy (and they may take profits on big down days and buy during the last hour). The other reason is the growth in leveraged ETF’s. A lot of the leveraged ETF’s needs to rebalance every day and this pushes more fuel to the fire. When the market goes up leveraged bull ETFs need to buy more to keep the leverage ratio. When the market drops, it’s the opposite effect, because bear ETF’s need to buy. However, this is not my field so I strongly urge you to read this research paper (thanks to Rob Hanna for making me aware of these articles). According to the mentioned research paper, as much as 10-50% on the MOC orders could be attributed to these ETF’s! Reading the research paper gave me new insights into how the markets work.