Exercise 2 solution

Years: 2014 - 1961 = 53.
Compound: (83/50)^(1/53) - 1 = about 0.0096, i.e. about 0.96 percent a year.
Straight line: (83 - 50) / 53 = 0.623 million a year; 0.623 / 50 = about 1.2 percent a year.
The article says 1.3 percent. Neither method gives exactly that.

Possible reason: the article may average the growth rates of each separate year (which gives a different answer from a rate based on endpoints), or use a different method or start values. That is a guess; the yearly data would be needed to test it.