Circular Flow of Income

Internal Flow

To understand how macroeconomics works, it is useful to imagine the economy as a system of flows — flows of money, goods, and services that continually circulate between various sectors. The circular flow of income model is a simplified yet powerful scheme that shows how the main participants in the economy are interconnected.

In the simplest model, the economy consists of two main sectors:

Firms — these are organizations that hire factors of production (labor, capital, land) and use them to produce goods and services. From a small cafe to a multinational corporation like Apple or Gazprom, all of them belong to the firms sector. Firms are employers and producers.

Households — these are individuals and families who, on the one hand, supply factors of production (working for firms, renting out land or premises, investing capital), and on the other hand, consume the goods and services produced by firms. Importantly, even a single student economically constitutes a "household."

Between firms and households there are two counter flows forming a closed cycle:

Flow 1: Factor Payments (from firms to households). Firms pay households for the use of their resources: wages and salaries — for labor, rent — for the use of land and premises, dividends — for invested capital (shares), interest — for loans provided. These are the incomes of households. In the United Kingdom, for example, wages make up about 55% of national income, profits and mixed incomes — about 25%, rent — about 10%.

Flow 2: Consumer Expenditures (from households to firms). Households spend their incomes on purchasing goods and services produced by firms. These expenditures become the revenue of firms, from which they again pay wages, rent, etc. Thus, the cycle closes.

Imagine it as two pipelines: along one, money flows from firms to households (wages), along the other — back from households to firms (spending on goods). If both "pipelines" operate stably, the economy is in equilibrium. But in reality, there are "leakages" and "injections," which disrupt this balance.

Leakages / Withdrawals — W

Not all income that households receive from firms returns back to firms in the form of consumer spending on domestic goods. Part of the income "leaks" out of the internal circular flow. These leakages reduce the flow of expenditures in the economy and, if not offset, lead to a decrease in national income.

Net Savings (S — Savings). Part of the income households set aside instead of spending. They deposit money into bank accounts, buy bonds, or simply stash cash "under the mattress." This money temporarily exits the circular flow — it doesn't turn into spending on goods and services. The savings rate varies greatly between countries: in China, households save about 30% of income (one of the highest rates in the world), in the USA — about 7%, and at some periods Americans saved less than 3% of income.

Why do people save? For purchasing expensive things in the future (apartment, car), for unforeseen circumstances (job loss, illness), for retirement, for passing on an inheritance. The level of savings depends on interest rates, confidence in the future, cultural factors, and government policy.

Net Taxes (T — Taxes net of transfers). Households and firms pay taxes to the government — income tax, VAT, corporate tax, social contributions, and others. This money is withdrawn from the circular flow and goes into the government budget. "Net" taxes are taxes minus transfer payments (pensions, unemployment benefits, social payments), because transfers return money to households. For example, if the government collects 40 billion in taxes and pays out 15 billion in pensions and benefits, net taxes are 25 billion.

In Scandinavian countries (Denmark, Sweden), the tax burden reaches 45–50% of GDP — these are among the highest figures in the world. In the USA — about 27%, in Russia — about 33%.

Spending on Imports (M — Imports). When households buy imported goods (Japanese car, Chinese smartphone, Italian pasta), the money leaves the country and does not return to domestic firms. This is a leakage from the internal circular flow. For some countries, imports are a very significant share of expenditures: for example, for Singapore imports exceed 150% of GDP (the country imports raw materials, processes them, and re-exports).

Total Leakages: W = S + T + M

Injections — J

Fortunately, there are also "injections" — expenditures that enter the circular flow from outside the internal stream between households and firms. They increase aggregate spending and offset (fully or partially) leakages.

Investment (I — Investment). Firms' expenditures on domestically produced capital goods — equipment, buildings, transport, technology. When a car factory buys a new conveyor, an IT company builds a new data center, or a retailer opens a new store — these are investments. They go to firms producing capital goods, those pay wages to their workers, and money returns to the circular flow. The level of investment strongly depends on interest rates (the lower the rates, the cheaper the loans, and the higher the investment), business expectations (if firms are optimistic about the future, they invest more), and technological possibilities.

Government Spending (G — Government Spending). The state spends money on goods and services: building roads and schools, paying salaries to teachers and doctors, purchasing military equipment, funding scientific research. These expenditures go to firms and workers, increasing aggregate demand. For example, when the UK government funds the construction of the high-speed railway HS2 (budget — over £100 billion), this is a massive injection into the economy: construction companies get contracts, hire workers, buy materials.

Spending on Exports (X — Exports). When foreigners buy domestic goods and services, money enters the economy from outside. For Germany, exports of cars (BMW, Mercedes, Volkswagen), industrial equipment, and chemicals are the main source of economic growth. For Russia, exports of oil and gas traditionally constitute a significant part of economic income.

Total Injections: J = I + G + X

<div style="text-align: center; margin: 20px 0;"> <svg width="100%" style="max-width: 600px;" viewBox="0 0 560 420" xmlns="http://www.w3.org/2000/svg"> <defs> <marker id="m6-arr2" markerWidth="8" markerHeight="6" refX="8" refY="3" orient="auto"> <polygon points="0 0, 8 3, 0 6" fill="#333" /> </marker> <marker id="m6-arr2b" markerWidth="8" markerHeight="6" refX="8" refY="3" orient="auto"> <polygon points="0 0, 8 3, 0 6" fill="#2563eb" /> </marker> <marker id="m6-arr2r" markerWidth="8" markerHeight="6" refX="8" refY="3" orient="auto"> <polygon points="0 0, 8 3, 0 6" fill="#dc2626" /> </marker> <marker id="m6-arr2g" markerWidth="8" markerHeight="6" refX="8" refY="3" orient="auto"> <polygon points="0 0, 8 3, 0 6" fill="#16a34a" /> </marker> </defs> <rect x="60" y="160" width="140" height="60" rx="6" fill="#f0f9ff" stroke="#2563eb" stroke-width="1.5" /> <text x="130" y="195" font-family="sans-serif" font-size="13" fill="#1e40af" text-anchor="middle" font-weight="bold">Households</text> <rect x="360" y="160" width="140" height="60" rx="6" fill="#fef2f2" stroke="#dc2626" stroke-width="1.5" /> <text x="430" y="195" font-family="sans-serif" font-size="13" fill="#991b1b" text-anchor="middle" font-weight="bold">Firms</text> <path d="M 200,175 C 260,140 300,140 360,175" stroke="#333" stroke-width="1.5" fill="none" marker-end="url(#m6-arr2)" /> <text x="280" y="148" font-family="sans-serif" font-size="10" fill="#333" text-anchor="middle">Consumer Expenditures (C)</text> <path d="M 360,205 C 300,240 260,240 200,205" stroke="#333" stroke-width="1.5" fill="none" marker-end="url(#m6-arr2)" /> <text x="280" y="255" font-family="sans-serif" font-size="10" fill="#333" text-anchor="middle">Factor Incomes (Y)</text> <line x1="130" y1="160" x2="130" y2="60" stroke="#dc2626" stroke-width="1.5" marker-end="url(#m6-arr2r)" /> <text x="135" y="55" font-family="sans-serif" font-size="10" fill="#dc2626" font-weight="bold">Savings (S)</text> <line x1="130" y1="220" x2="130" y2="310" stroke="#dc2626" stroke-width="1.5" marker-end="url(#m6-arr2r)" /> <text x="135" y="325" font-family="sans-serif" font-size="10" fill="#dc2626" font-weight="bold">Taxes (T)</text> <line x1="60" y1="190" x2="10" y2="190" stroke="#dc2626" stroke-width="1.5" marker-end="url(#m6-arr2r)" /> <text x="35" y="210" font-family="sans-serif" font-size="10" fill="#dc2626" font-weight="bold" text-anchor="middle">Imports (M)</text> <text x="90" y="360" font-family="sans-serif" font-size="11" fill="#dc2626" font-weight="bold">Leakages (W = S + T + M)</text> <line x1="430" y1="160" x2="430" y2="60" stroke="#16a34a" stroke-width="1.5" marker-end="url(#m6-arr2g)" /> <text x="430" y="48" font-family="sans-serif" font-size="10" fill="#16a34a" font-weight="bold" text-anchor="middle">Investment (I)</text> <line x1="430" y1="220" x2="430" y2="310" stroke="#16a34a" stroke-width="1.5" marker-end="url(#m6-arr2g)" /> <text x="430" y="325" font-family="sans-serif" font-size="10" fill="#16a34a" font-weight="bold" text-anchor="middle">Gov. Spending (G)</text> <line x1="500" y1="190" x2="550" y2="190" stroke="#16a34a" stroke-width="1.5" marker-end="url(#m6-arr2g)" /> <text x="525" y="210" font-family="sans-serif" font-size="10" fill="#16a34a" font-weight="bold" text-anchor="middle">Exports (X)</text> <text x="430" y="360" font-family="sans-serif" font-size="11" fill="#16a34a" font-weight="bold" text-anchor="middle">Injections (J = I + G + X)</text> <text x="280" y="405" font-family="sans-serif" font-size="12" fill="#555" font-style="italic" text-anchor="middle">Fig. 1: Extended Circular Flow of Income</text> </svg> </div>

Relationship Between Leakages and Injections

There are indirect links between leakages and injections through institutions:

• Savings (S) → Investment (I): Banks and financial institutions accept household savings and lend to firms for investment. Thus, money "leaked" from the circular flow through savings can return via investment. However, there is no guarantee that banks will direct all savings to loans — they may create reserves, or firms may not want to borrow.

• Taxes (T) → Government Spending (G): The government collects taxes and spends them for government purposes. If G = T, the budget is balanced. If G > T, the government spends more than it collects (budget deficit). If G < T, the government has a budget surplus.

• Imports (M) → Exports (X): Money spent on imports goes to other countries, but those countries, in turn, may buy our exports. If X = M, the trade balance is balanced. In practice, most countries have either a deficit (M > X, as in the USA), or a surplus (X > M, as in Germany or China).

Important: Planned injections (J) may not equal planned leakages (W). There is no automatic mechanism guaranteeing their equality. This is fundamentally important: if J ≠ W, the economy is not in equilibrium, and national income will change.

Equilibrium in the Circular Flow

Equilibrium Condition

The economy is in equilibrium when injections equal leakages:

J = W, that is, I + G + X = S + T + M

Or, in more familiar notation: Y = C + I + G + X − M (national income is equal to aggregate expenditures).

When the economy is in equilibrium, there is no tendency for national income to change — it remains stable.

When J ≠ W — Disequilibrium

If J > W (injections exceed leakages), aggregate expenditures grow, and national income increases. More money flows into the economy than leaks out. Firms sell more, hire more workers, pay more wages, households spend more — a chain reaction of growth starts.

Real example: in 2020–2021, governments of many countries sharply increased government spending (G) to fight the consequences of the pandemic, while taxes (T) were not raised. Injections significantly exceeded leakages, which led to rapid growth in aggregate demand and, subsequently, to inflation in 2022–2023.

If J < W (leakages exceed injections), aggregate expenditures fall, and national income decreases. More money leaks out of the economy than is injected. Firms sell less, cut production, lay off workers — a recession begins.

Real example: during the 2008 financial crisis, investment (I) dropped sharply (firms were afraid to invest in uncertain conditions), consumers sharply increased savings (S) out of fear of losing their jobs, and exports (X) declined due to global demand contraction. Leakages significantly exceeded injections, which led to a deep recession.

Multiplier Effect

One of the most important discoveries in macroeconomics (associated with John Maynard Keynes) is that an initial change in injections causes a multiple (multiplier) change in national income. This is called the multiplier effect.

How does it work? Suppose the government decides to spend an additional 100 million rubles on building a bridge. This money is received by construction companies, which pay wages to workers. If workers spend 80% of their income on consumption (marginal propensity to consume MPC = 0.8), they spend 80 million rubles in shops and restaurants. Shop and restaurant owners get these 80 million, spend 80% of it (64 million), and so on. Each "round" of spending creates new incomes, although each subsequent round is smaller than the previous.

The total increase in national income: 100 + 80 + 64 + 51.2 + 40.96 + ... = 100 × 1/(1 − 0.8) = 100 × 5 = 500 million rubles

Multiplier (k) = 1 / (1 − MPC) = 1 / MPS, where MPS is the marginal propensity to save.

In our example: k = 1 / (1 − 0.8) = 1 / 0.2 = 5. That is, every ruble of government spending creates 5 rubles of additional national income. In practice, the multiplier is usually much smaller, because part of the income leaks not only through savings, but also through taxes and imports.

A more realistic formula: k = 1 / (MPS + MPT + MPM), where MPT is the marginal tax rate, MPM is the marginal propensity to import. If MPS = 0.1, MPT = 0.2, MPM = 0.2, then k = 1 / (0.1 + 0.2 + 0.2) = 1 / 0.5 = 2. This means that 100 million of government spending will increase national income by 200 million — still a significant effect, but not as dramatic.

Three Sides of National Income

National income can be measured from three sides, and all three give the same result. This is a fundamental identity in macroeconomics:

1. Output — the sum of added value of all industries. How many goods and services did the economy produce?

2. Income — the sum of all factor incomes: wages, rent, profit, interest, dividends. How much did all participants in production earn?

3. Expenditure — the sum of all spending on final products: C + I + G + X − M. How much has been spent on purchasing produced goods?

All three methods give the same result, because these are three views of the same thing. Every product produced (output) yields income to someone (income) and is purchased by someone (expenditure). If a bakery produced bread worth 100 rubles (output), from these 100 rubles the baker received wages, the owner got profit, the landlord — rent (income), and someone spent 100 rubles to buy the bread (expenditure).

What is NOT factor income: Sale by a firm of a used car — this is a capital transaction (redistribution of an existing asset), not income from participation in current production. Wages, rent, profit, salaries, dividends are factor incomes.

Practical Exercises

Problem 1: Multiplier

Question: The marginal propensity to consume (MPC) in the economy = 0.75. Marginal tax rate (MPT) = 0.2. Marginal propensity to import (MPM) = 0.15. (a) Calculate the multiplier. (b) If the government increases spending by £500 million, by how much will national income grow? (c) Explain why the real multiplier is smaller than the simple multiplier 1/(1-MPC).

Solution: (a) MPS = 1 - MPC = 1 - 0.75 = 0.25. Multiplier k = 1 / (MPS + MPT + MPM) = 1 / (0.25 + 0.2 + 0.15) = 1 / 0.6 ≈ 1.67.

(b) Change in national income = k x change in injection = 1.67 x £500 million = £835 million.

(c) Simple multiplier = 1 / (1 - MPC) = 1 / 0.25 = 4 — but it assumes that the only leakage is savings. In reality, part of the income also "leaks" through taxes (MPT = 0.2 → 20% of each additional pound is taken by the government) and imports (MPM = 0.15 → 15% is spent on foreign goods, not creating income within the country). These extra leakages reduce each "round" of spending, significantly lowering the multiplier effect from 4 to 1.67.

Problem 2: Leakages and Injections

Question: Determine whether each of the following is a withdrawal (leakage) or an injection in the circular flow model:

A. Russian firm exports gas to Europe B. Household transfers 20% of salary to a savings account C. Government builds a new highway D. Consumer buys an iPhone manufactured in China E. Foreign company builds a factory in Russia

Solution: A. Injection (X — export). Money enters the economy from foreign gas buyers.

B. Leakage (S — savings). Money is withdrawn from the flow of expenditures and does not directly return to firms.

C. Injection (G — government spending). Money is injected into the economy: construction companies receive revenue, pay wages, buy materials.

D. Leakage (M — import). Money leaves the national economy to a foreign producer (Apple/Foxconn in China).

E. Injection (I — investment). Foreign direct investment injects capital into the economy, creates jobs, and generates incomes.