I really have no way of backtesting this, but hear me out. Say you can generate $1000 a month to invest regularly. Now lets say you buy 1 share of SPY on every down day in the market. At 3:55pm if the S&P is down, you buy 1 share. Sure some months you would not have enough negative days to invest your entire $1000, but certainly other months would make up for it. What kind of returns do you think you would see long term? I know it sounds a little juvenile and oversimplified, just curious...