Well, they're usually revising/improving their models while the robots print money today to ensure that the robots can print more money tomorrow. The frequency

Well, they're usually revising/improving their models while the robots print money today to ensure that the robots can print more money tomorrow. The frequency and depth of the human input varies based on the kind of strategies employed (macro/statistical arbitrage etc). Moreover, successful models take competitors' potential models into account which (like everything else) is a moving target.