Final answer:
In a table converted to percentages, the cumulative column must add up to 100% because it represents the entire distribution of a population's metrics (like income), with each segment (quintile) contributing to this total.
Step-by-step explanation:
When converting a table with two columns into percentages, the final values in the column representing the cumulative percentage will always add up to 100%. This is because the cumulative percentage represents the total distribution up to that point, and by definition, the entirety of a population will have distributed among it 100% of whatever is being measured—such as income. When dealing with quintiles, or any other divisions of the data, each segment's contribution is added together to reach the cumulative total. For example, the bottom 40% of the cumulative income distribution would be the sum of the first and second quintiles, while the bottom 60% would be the sum of the first, second, and third quintiles, and so on until the sequence is complete and the final entry is 100%.
The calculation of income distribution works in this way: each quintile's percentage is divided by the total and then multiplied by one hundred to get the percent value. When filling in a table with this data, and providing relative frequencies, it is important to show work and round answers to at least two decimal places to confirm accuracy beyond just copying table results.