I have build a city growth/diminish model based on few parameters to be used for real estate prices predictions, growth means demand and diminish means supply. One of these parameters is the usage of electricity for industrial purposes, meaning economy, jobs, people and demand. But the same reasoning can be "mapped" to a country level. I.e. how much electricity is being consumed in a country as a function of time, is a good measure, or at least one of the indicators, of the economy of that country. Below I show the the US and China generation of electricity over the last couple decades.
We need to keep in mind that China has four time the population of the USA, so we cannot look at the graph above in nominal terms. What we are looking at is the growth of the usage and the slope (velocity) of the growth. We an see how post 2000, China has shifted gears. That is also consistent with the urbanization of China, that led to additional demand.