Final answer:
The size distribution of income is the better indicator to measure and understand income inequality today.
Step-by-step explanation:
The better indicator to measure and understand income inequality today is the size distribution of income. This is because it considers the entire population and divides it into groups, such as quintiles, to calculate the share of income received by each group. In contrast, the functional distribution of income focuses on the social class and does not provide a comprehensive view of the income distribution.