Using the rank-size rule, if the largest city in a country has a population of 8,000,000, what would be the expected population of the 4th ranked city?

The rank-size rule states that the population of a city of rank $r$ is equal to the population of the largest city divided by its rank: $P_r = P_1 / r$. For the 4th ranked city: $P_4 = 8,000,000 / 4 = 2,000,000$. Option A (4,000,000) corresponds to rank 2, Option B (2,666,667) to rank 3, and Option D (1,600,000) to rank 5, representing common rank substitution errors.