The decile ratio is a measure of inequality that shows what percentage of the income in an economy goes to the richest 10% of the people. It’s calculated by dividing the share of national income going to the richest 1% of households by the share going to the poorest 10%. When this ratio is greater than 10 or 20, inequality is increasing.

The decile coefficient (also known as the coefficient of income differentiation) is an indicator of social statistics that shows the level of social stratification among the people of a particular state by showing how much 10% of the minimum income of wealthy people is greater than 10% of the income of the less wealthy. An income ratio of this kind can only approximate the stratification of society since it is impossible to accurately calculate this 10% for the entire country, and even their income can only be approximately and a larger part overall.

First you need to find the 1st decile - that is, the income of 10% of the less wealthy population and the 9th decile, which is the income level of 10% of the population with higher incomes. Decile ratio equals the ratio of the 9th decile to the 1st decile.