What really causes falling productivity growth? The answer seems to be very much energy-related. Human labor by itself does not cause productivity growth. It is human labor, leveraged by various tools, that leads to productivity growth. These tools are made using energy, and they often use energy to operate. A decrease in energy consumption by the business sector can be expected to lead to falling productivity growth. In this post, I will explain why such a pattern can be expected, and show that, in fact, such a pattern is happening in the United States.