Identify which of the following is a flow variable:

1. Inventory
2. Wealth
3. Income
4. Change in inventories

Choose the correct answer from the options given below:

C and D only

Stock variables are those variables which are measured at a particular POINT of time whereas, flow variables are those variables which are measured over a PERIOD of time. Losses incurred by a firm is measured over a PERIOD of time thus considered as a "Flow variable", whereas, Bank deposits as on 1st oct 2017, Money supply etc are measured on a POINT of time thus, will be considered as a stock variable. In the above question, as, income and change in inventories are calculated over a period of time thus, it will be considered as a "Flow variable".