The rich/poor ratio introduced in this context is conceptually similar to—but not identical to—a widely recognized measure of inequality known as the 90/10 ratio. The 90/10 ratio is calculated as the ratio of the income of an individual at the ninetieth percentile to that of an individual at the tenth percentile. In contrast, the rich/poor ratio compares the average income of the top decile (the "rich") to that of the bottom decile (the "poor").

The key distinction lies in the composition of the deciles. The top decile encompasses all individuals whose income exceeds that of the person at the ninetieth percentile, resulting in an average that is higher than the income of the individual at that percentile. Similarly, the bottom decile consists of all individuals with income below that of the person at the tenth percentile, yielding an average that is lower than the income of the individual at that percentile. Consequently, the rich/poor ratio tends to yield a larger value than the 90/10 ratio for a given country.