The per capita income figure published by the government may not be exact, but it does present a fairly accurate picture. Since a considerable segment of the population falls below the minimum income level for filing income tax, it is hard to keep track of their incomes, and consequently, they are represented statistically as if they had no income. However, one must keep in mind that a large number of the wealthy also have a tendency to understate their income.
Which of the following is an assumption on which the argument above depends?