If a HFT firm makes a profit then they are, by definition, adding value to the economy.
All that technology investment is not a waste; it allows firms to condense money out of information asymmetries with ever greater efficiency.
Edit to add: if you prefer industries that build "real things" then look at the revenue that HFT delivers to companies who make high-speed networking and computer equipment.
All that technology investment is not a waste; it allows firms to condense money out of information asymmetries with ever greater efficiency.
Edit to add: if you prefer industries that build "real things" then look at the revenue that HFT delivers to companies who make high-speed networking and computer equipment.