They are similar to a market maker but it's not the same. They are like predatory HFT, benefiting from fast information propagation. Most of the time the market

They are similar to a market maker but it's not the same. They are like predatory HFT, benefiting from fast information propagation. Most of the time the market would function well without them, with much less volatility in the price. In that sense, scalpers en masse are destabilizing the economy.