Anumber of highly regarded business people and politicians, including Microsoft founder Bill Gates and NYC Mayor Bill De Blasio, have commented on the potential need for a “robot tax.” Interest in such a tax appears to be founded on the belief that robots, and automation more generally, will lead to large job losses. The basic idea behind a robot tax is that firms pay a tax when they replace a human worker with a robot. Such a tax would in theory have two main purposes. First, it would disincentivize firms from replacing workers with robots, thereby maintaining human employment. Second, if the replacement were made anyway, a robot tax would generate revenues for the government that would cover the loss of revenue from payroll taxes. Some proponents of a robot tax also suggest that the revenue could then be used for worker re-training programs or other forms of support for the displaced worker.