Check out the graph about halfway down in that article. It’s revelatory.
If you had bought the SPY at the last second of trading on each business day since 1993 and sold at the market open the next day — capturing all of the net after-hour gains — your cumulative price gain would be 571 percent.
On the other hand, if you had done the reverse, buying the E.T.F. at the first second of regular trading every morning at 9:30 a.m. and selling at the 4 p.m. close, you would be down 4.4 percent since 1993.
I had no idea of this fact and thought it was quite interesting.