The term "To each according to his contribution" simply means that each worker in a socialist society receives "wages" and benefits according to the quantity and value of the labor that he or she contributed. That way, highly productive workers will receive more wages and benefits than workers of average productivity, and substantially more than workers of low productivity. What is more, the more difficult the job is, the more one is rewarded for the labor contributed. Difficulty can result from factors such as greater training requirement, job intensity or safety hazards. According to Trotsky, the idea is to promote productivity. This is done by creating incentives to work harder, longer, and more productively. In the end, the principle comes from capitalism, but will vanish, according to Marx, as work becomes more automated and enjoyable, and as goods become available in greater quantities.