During the past century the average growth rate of U.S. real GDP per person implies that it doubled, on average, about every

Question

a.

25 years.
b.

100 years.
c.

70 years.
d.

35 years.

Answer 1

To determine how long it takes for something to double, we can use the Rule of 70, which states that you can approximate the number of years it takes for an investment to double by dividing 70 by the growth rate (expressed as a percentage).

If we consider the average growth rate of U.S. real GDP per person over the last century to be around 2% per year (which is a reasonable historical estimate for long-term GDP growth), we can calculate it as follows:

Years to double = 70 / growth rate

Assuming a growth rate of 2%:

Years to double = 70 / 2 = 35 years.

Therefore, the answer is:

d. 35 years.