In the stock market, program trading dominates volume. I heard recently that 70% of trade positions are held for an average of 11 seconds.
As the New York Times dealbook noted in May:
These are short-term bets. Very short. The founder of Tradebot, in Kansas City, Mo., told students in 2008 that his firm typically held stocks for 11 seconds. Tradebot, one of the biggest high-frequency traders around, had not had a losing day in four years, he said
Similarly, FT’s Martin Wheatley pointed out last month:
I know of one HFT firm operated out of the west coast of the US that boasts its average holding period for US equities is 11 seconds.