[teabee89]

>> Why is US GDP growth so weirdly constant?

> My guess is energy.

Your guess is correct. Energy is what drives the economy. We've been going from least concentrated to most concentrated energy sources: human/animal muscle to wind, river flow, to coal, oil, nuclear. Oil being the best tradeoff between ready-to-use and energy concentration. GDP is what people are paid, but the people have magical machines that run on energy.

Any bell curve looks exponential in the beginning, but when you run out of that concentrated energy you're left with less concentrated energy unable to sustain the same level of growth.