How Much Does the Stock Market Move During the Day?

Very cool video courtesy of @nanexllc on Twitter.

X-Axis is hour of day between 0 and 24 (midnight to midnight Eastern Time) Y-Axis is price change in percent from 1 hour ago. Each line shows how much the stock market moves (in percent) over the last hour during 1 trading day. The price of the active S&P 500 futures contract (the EMini) is used as a proxy of the U.S. stock market. The EMini has been the benchmark price of the U.S. market since the 1980s. Note: the U.S. market opens at 9:30 and closes at 16:00. The EMini trades 24 hours (except for daily maintenance halts between 16:15 and 18:00). High Frequency Trading (HFT) came about in 2007: has volatility increased or decreased from that time? Note the extreme volatility during the financial crisis (Fall 2008), around the time of the flash crash (May 6, 2010), during the US Debt downgrade (August 2011) and during the US Treasury flash crash (Oct 15, 2014)