Exercise 1 solution

All sums checked in Python.

(a) 85 + 7 + 8 = 100, so the shares cover everything. The share between groups is 7 + 8 = 15 percent: about 7 percent between populations on the same continent and about 8 percent between continents. The other 85 percent lies within local populations.

(b) 85 - 81 = 4 percentage points, over 2024 - 2003 = 21 years. That is about 0.19 points a year (4 / 21 = 0.19, rounded). For comparison, the chapter's earlier figures were 56 percent in 1963 and 79 percent in 2016: 23 points over 53 years, about 0.43 a year, so the later period moved more slowly on these numbers. Both pairs come from the Gender pay gap page as I read it.

(c) If women earn 85 for every 100 men earn, the gap is 100 - 85 = 15, which is 15 percent of men's earnings. Men earn 100 / 85 = 1.176, so about 17.6 percent more than women.

(d) The two numbers use different bases. The first divides the difference (15) by what men earn (100); the second divides the same difference by what women earn (85). One fact, two denominators. When a report quotes a "gap", check which group it is measured against.