Answer:
For certain, simple tasks—such as garbage collection and painting barns—a socialist government could use punishment to get workers to carry out their assigned duties. But many jobs require creativity and other unobservable aptitudes. A market economy allows workers to choose their own occupations and discover the fields where they can contribute the most. Even with the use of punishment, socialist officials wouldn't be able to force their subjects to produce the same output. (Could you really use a whip to force someone with nimble hands to spend years training to become a brain surgeon?)