Whenever markets suffer a bout of volatility, someone blames high-frequency traders. In the bumpy last months of 2018, US Treasury Secretary Steven Mnuchin urged a government investigation of high-speed trading. After the recent August chop, some said the exit of traditional dealers from market-making had hurt stock-trading liquidity.

And when someone blames high-frequency traders for causing market volatility, the data nerds at Citadel Securities fire up a study. Citadel’s latest study examines whether stock-trading liquidity on exchanges has declined and aggravated the market’s mood swings. The firm concludes it has not.