The chart would also look the same way if you overpaid it with deregulation or tax cuts for that matter. After all in the 1940s the tax rate was 90% and energy cost was 2 cents a kWh. 1960s down to 70% and up to 3. 80s down to 45% up to 4. Now 37% and .17. Making a graph is easy- understanding the actual drivers is harder.