Q.Classify each of the following as a STOCK variable or a FLOW variable, giving a one-line reason for each:

Ask whether each variable is measured AT A POINT in time (stock) or OVER A PERIOD (flow) — a time dimension like 'per month' or 'during the year' signals a flow.

(i) Stock — measured 'as on' a date. (ii) Flow — 'per month'. (iii) Stock — owned 'today', a point in time. (iv) Flow — 'during the year'. (v) Stock — 'on the census date'.

The test in each case is whether the variable is measured at a PARTICULAR POINT in time (a stock) or OVER A PERIOD of time (a flow — signalled by phrases like 'per month' or 'during the year').

1. Stock. The money in a bank account 'as on 31st March' is an amount existing at a single instant — a snapshot — so it is a stock variable.
2. Flow. A salary of ₹30,000 'per month' carries a time dimension (per month); it measures income earned over a period, so it is a flow variable.
3. Stock. The total capital a factory owns 'today' is the amount of assets in existence at one point in time — a stock.
4. Flow. Investment made 'during the financial year' is the addition to capital over a period; it carries a time dimension, so it is a flow. (Note how this flow, accumulated, changes the capital stock in (iii).)
5. Stock. A country's population 'on the census date' is the number of people existing at one moment — a stock.
   ✓Final answer

   Stocks (measured at a point in time): (i), (iii), (v). Flows (measured over a period): (ii), (iv). The presence of a time dimension such as 'per month' or 'during the year' is the clearest sign of a flow.

The commonest error is treating any large money amount as a 'stock' and any small one as a 'flow', or the reverse — size is irrelevant. The only correct test is whether the variable is measured at a point in time (stock) or over a period of time (flow); a monthly salary is a flow even though it is a fixed sum of money.