Interesting datapoints (summarized on reddit):<p>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.<p>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<p>Chart: <a href="https://i.imgur.com/YPTjg3v.jpg" rel="nofollow">https://i.imgur.com/YPTjg3v.jpg</a>