Which of the following is a flow variable?

A flow variable measures a quantity at a specific point in time, whereas a stock variable measures a quantity accumulated over time. Income is classified as a flow variable because it is generated over a period (e.g., earned weekly, monthly, or annually) and reflects the amount of money coming into a household or entity over that time frame. This means that income can vary from one period to another, highlighting its dynamic nature.

In contrast, wealth, the number unemployed, and government debt are stock variables. Wealth represents the total assets held at a specific moment, the number unemployed indicates a count of individuals without jobs at a particular time, and government debt reflects the total outstanding liabilities of the government at a given time. These variables do not capture the concept of a rate or total that accumulates over a defined period, which is why income stands out as the correct choice for a flow variable.