The primary benefit was that it decreased transaction costs  which is the reason spreads went down in the late 90s&#x2F;early 00s when humans were still in the loop.<p>Humans are of course perfectly capable of rigging the market with or without computers, a fact so mind-blowingly obvious, I&#x27;m not sure why you&#x27;d accuse someone of believing that it&#x27;s false.<p>This particular thread was not about market rigging, it was about whether HFT can really be credited with decreasing spreads in the early 00s.