Stocks and flows

A flow is measured over an interval, so “during a period” is the most suitable expression. Income, expenditure, production, and investment are flows because they occur through time. “On a date,” “today,” and “at year end” generally identify a point-in-time stock or balance.

The fundamental distinction is the time dimension of measurement. A stock is measured at a particular instant, such as wealth or debt on 31 March. A flow is measured across an interval, such as income, expenditure, or production during a year. The other statements wrongly restrict the concepts or make an unsupported numerical claim.

Cash balance today is the amount held at a particular point in time, so it is a stock. Expenditure during the week is the total spending accumulated over a specified interval, so it is a flow. The fact that both are expressed in money does not make them the same type; the measurement period determines the classification.

Accounts receivable on a particular date represents the amount outstanding at one point in time, so it is a stock. Credit sales during the year represent transactions accumulated over a period, so they are a flow. The words “on a date” indicate a stock, while “during the year” indicates a flow. Therefore, option A is correct.

Government borrowing during the year is measured over a time interval and records a transaction occurring during that period; therefore, it is a flow. Total government debt at the end of the year is the accumulated outstanding liability at one specific date, so it is a stock. Hence the correct order is flow and stock, option B.

Money supply means the quantity of money existing and available in the economy at a particular point in time, so it is a stock variable. New money creation refers to the amount added during a specified period, such as a year, and is therefore a flow. Thus, the correct classification is stock and flow, option C.

Outstanding share capital at the end of the year is the accumulated value existing on a particular date, so it is a stock. The value of new shares issued during the year records an addition occurring over a period, so it is a flow. The first quantity is therefore a stock and the second is a flow. Hence, option B is correct.

A bank balance on a particular date shows the amount held at one point in time. It is therefore a stock, not a flow. Interest earned during a month, sales during a year, and output produced during a week are all measured over intervals of time and are flows. The date-based bank balance is the only correct exception, so option A is correct.

Monthly consumption expenditure is the total spending incurred throughout one month. Because it is measured over a period, it is a flow rather than a stock. Wealth at year end, debt today, and capital on a particular date are measured at specific points in time and are stocks. Therefore, option C is the only correct answer.

The number of books the student has today is measured at one particular point in time, so it is a stock. The number of books bought during the year counts acquisitions occurring over a period, so it is a flow. The example illustrates that even a physical quantity can be classified by its time reference.

The number of hospital beds available on a particular day describes capacity existing at one point in time, so it is a stock. The number of patients admitted during a month counts events occurring throughout a time interval, so it is a flow. Since the order is stock followed by flow, option B is correct.

Debt repayment during the year records payments made over a period, so it is a flow. Debt outstanding at the end of the year represents the remaining liability on one specific date, so it is a stock. The repayment may reduce the debt stock, but the repayment amount itself is still a flow. Therefore, the correct order is flow and stock, option A.

Annual sales measure the value of transactions completed throughout an entire year, so sales are a flow. Accounts receivable at year end measures the unpaid amount outstanding on one particular date, so it is a stock. The time expressions identify the classification: “annual” indicates a period, while “at year end” indicates a point in time. Hence, option A is correct.

The goods stored in a warehouse today represent the quantity existing at a particular point in time, so they are a stock. Withdrawals during the day count movements or transactions occurring throughout a period, so they are a flow. The correct order is therefore stock and flow. Option B accurately applies the time-based definitions.

The most reliable test is the time dimension. A stock is measured at a particular point, such as wealth on 31 March, whereas a flow is measured over a period, such as income earned during a year. The size, name, or government ownership of an item does not determine its classification. Therefore, option D is correct.

Borrowing during the year is measured over a specified period, from the beginning to the end of the year. Therefore, it is a flow variable. Total external debt at the end of the year represents the accumulated outstanding liability at one particular point in time, so it is a stock variable. The correct order is therefore flow and stock, as stated in option A. This distinction is important because flows change stocks over time.

The value of machinery at year-end is measured on a particular date and represents the capital asset held at that time; it is therefore a stock. Depreciation during the year measures the loss in value over a period and is therefore a flow. Hence, option C gives the correct order.

Opening capital stock is the value of machines, buildings, and other capital assets available at the beginning of a specified year. Since it is measured at one point in time rather than over the whole year, it is a stock variable. Net investment, in contrast, is measured during the year and is a flow.

Net investment during the year measures the addition to, or change in, the capital stock over a particular period. Since it is recorded for the whole year, it is a flow variable. A capital stock or accumulated wealth, in contrast, is measured at a particular point in time and is therefore a stock. The phrase “during the year” is the key clue. Hence, option B is correct.

National income is the income generated or earned during a specified period, such as a year, so it is a flow. National wealth is the accumulated value of assets owned by a nation and measured at a particular date, so it is a stock. Therefore, option B correctly distinguishes them.

Cash in hand at the end of the day states the amount available at one specified point in time, so it is a stock. Cash sales, receipts, and withdrawals during a month, year, or week are transactions accumulated over periods and are therefore flows. Hence, option C is the correct answer.

Cash receipts during a month are measured by adding all receipts that occur throughout that specified period, so they constitute a flow. A cash balance today, on a date, or at year-end is an amount existing at one point in time and is therefore a stock. Thus, option D is correct.

A company’s net worth on a particular date is the value of its assets minus its liabilities at that point in time. Because it describes a position on a date, it is a stock variable. Annual profit is calculated from revenue and expenses earned or incurred throughout the year, so it is measured over a period and is a flow variable. Thus, the correct order is stock and flow, given in option A.

Production capacity on a specified date represents the maximum productive capability available at that point in time. It is a position or existing capacity, not the quantity actually produced over a period. Therefore, it is a stock variable. Actual output during a year would be a flow, so option B is correct.

Annual output is the quantity or value of goods produced throughout one year. Because it is measured over a specified period rather than at one particular moment, it is a flow variable. A factory’s capacity or inventory on a particular date would be a stock, but annual production is correctly classified as a flow; therefore, option C is correct.