Thus, the fluctuating exchange value of commodities (exchangeable products) is regulated by their value, where the magnitude of their value is determined by the average quantity of human labour which is currently socially necessary to produce them (see labor theory of value and value-form). In itself, this theorem is fairly simple to understand, and intuitively it makes sense to many working people. Theorizing its implications is, however, a much more complex task; it kept Marx busy across more than two decades.