The average rate of growth for slow-growth countries is around 2% per year, and for fast-growth, greater than 5% per year. Suppose the growth rate of the economy is 2%. The size of the economy roughly doubles every 5 years. 20 years. 50 years or more. 35 years. 10 years. If instead the growth rate is 7%, the doubling time for the economy is 50 years or more. 35 years. 20 years. 5 years. 10 years. Economic growth is important to understand because it is closely tied to standard of living. growth guarantees that the rich get richer and the poor get poorer. understanding economic growth is key to getting a banking job after graduation. income equality cannot exist without growth.