People who are able to focus on their work because they can pay their bills, have good working conditions, are healthy and able to care for their families work better. Big surprise.
Of course there's an upper limit to this - if you're paying your apple pickers more than the retail price of the apples then you're going to be in trouble. But in those cases, the price of apples needs to be higher so that apple pickers can have some basic human dignity. Apples should cost more, but we have created an evil system that destroys apple pickers' lives so that the rest of us can have cheap apples. Let's not do that any more.