The Absorption Approach to the Balance of Payments

The absorption approach explains the current account balance as the difference between what an economy produces and what it spends. Sidney Alexander set it out in 1952 as a correction to the elasticities approach, which had analysed devaluation entirely through relative prices and the responsiveness of trade volumes to them.

Its contribution is a single identity that makes the constraint unavoidable, and once the identity is written down the policy conclusion follows without any further argument.

The identity

Start from national income:

Y = C + I + G + (X − M)

Define absorption A as total domestic spending: A = C + I + G. Then

Y = A + (X − M), so (X − M) = Y − A

The current account balance equals output minus absorption. A country in deficit is absorbing more than it produces; a country in surplus is producing more than it absorbs.

The identity is an accounting relationship and is true by construction. That is exactly what makes it powerful as a constraint: any policy claiming to improve the current account must either raise output or reduce absorption, because there is no third route.

What this says about devaluation

The elasticities approach asks whether a devaluation improves the trade balance by making exports cheaper abroad and imports dearer at home, and answers through the Marshall-Lerner condition: the sum of the elasticities of demand for exports and imports must exceed one.

The absorption approach asks a different question. A devaluation improves the current account only if it raises income relative to spending. Relative prices are the mechanism; the change in Y − A is the outcome, and if absorption rises as fast as output the balance does not move however responsive trade volumes are.

Two cases separate.

With unemployed resources. A devaluation shifts demand towards domestic goods, output rises, and if absorption rises by less than output the current account improves. This is the favourable case and it depends on spare capacity existing.

At full employment. Output cannot rise, so Y is fixed. Improving the balance requires absorption to fall, which means consumption, investment or government spending must be cut. A devaluation alone will not do it; it must be accompanied by an expenditure-reducing policy. This is the approach's central policy conclusion and the reason it was influential.

How absorption responds

Alexander identified several channels through which a devaluation affects absorption directly, and they do not all run the same way.

The real balance effect. Devaluation raises the domestic price level, which reduces the real value of money holdings. To restore them, people spend less. This reduces absorption and helps the balance.

Income redistribution. Inflation redistributes from wages to profits and from fixed-income groups to others. Because the propensity to save differs across these groups, the effect on aggregate absorption depends on who gains, and it is generally taken to reduce absorption where profits rise relative to wages.

Money illusion. If people respond to nominal rather than real changes, absorption may not adjust as the real balance effect predicts, weakening the mechanism.

The terms of trade. Devaluation usually worsens the terms of trade: more exports must be given up for the same imports. This reduces real income, which reduces absorption, but it also reduces the real resources available, so the effect on the balance is ambiguous.

The honest summary is that the direct effects on absorption are several, act in both directions, and are not large enough to rely on. The policy conclusion therefore rests on the identity rather than on the channels.

Against the elasticities approach

The two are not rivals in the way introductory accounts suggest, and saying so is worth a mark.

The elasticities approach is a partial-equilibrium analysis of the trade balance. It holds income constant and asks how volumes respond to prices. Its condition — Marshall-Lerner — is necessary for a devaluation to improve the balance through the price channel.

The absorption approach is a general-equilibrium accounting constraint. It allows income to change and asks what must be true of the whole economy.

A devaluation that satisfies Marshall-Lerner but is accompanied by an equal rise in absorption will not improve the current account. A devaluation that fails Marshall-Lerner in the short run may still improve it if absorption falls sharply. Both conditions matter, and the standard modern treatment combines them instead of choosing.

The monetary approach, developed later, goes further and treats a current account deficit as a monetary phenomenon reflecting an excess demand for money, which absorbs the earlier approaches into a still more general framework.

The J-curve, and why timing matters

The absorption identity says nothing about time, and observed devaluations frequently make the balance worse before improving it.

The reason is that contracts are priced in advance and volumes take time to adjust. Immediately after a devaluation, import prices rise while volumes are unchanged, so the import bill rises in domestic currency and the balance deteriorates. As volumes adjust over months or quarters, the balance improves and eventually exceeds its starting point, tracing a J.

In absorption terms this is a statement about the lag between the price change and the output response. Y rises slowly while the terms-of-trade deterioration hits immediately, so the initial movement in Y − A is adverse.

The practical implication is that a devaluation requires financing for the period before it works, which is precisely when confidence is weakest — a combination that has produced a good many programmes abandoned before the improvement arrived.

A worked illustration

An economy produces output of 500 and absorbs 530, so the current account deficit is 30.

Case one: spare capacity. A devaluation shifts demand towards domestic goods. Output rises to 540 as idle resources are employed. Absorption rises too, because higher incomes raise consumption — say to 545. The deficit falls from 30 to 5. The improvement came from output rising faster than spending, which is the favourable case.

Case two: full employment. Output is fixed at 500. The same devaluation cannot raise it. Unless absorption falls below 500, the deficit persists whatever happens to relative prices, and the excess demand shows up as inflation, not as improved trade. Closing a deficit of 30 requires cutting spending by 30, in some combination of consumption, investment and government.

Case three: absorption rises with the devaluation. Firms expecting higher export demand raise investment; the government increases spending to offset the cost-of-living effect. Output rises to 540 and absorption to 575. The deficit widens to 35 despite a devaluation that satisfied every elasticity condition.

The third case is the one the approach exists to make visible, and it is not hypothetical: devaluations accompanied by expansionary policy have repeatedly failed to improve the balance, and the elasticities framework has no way of explaining why.

What it implies for policy design

The framework produces a two-instrument conclusion that became standard.

Expenditure switching — devaluation, tariffs, quotas — moves demand between domestic and foreign goods. It works on the composition of spending.

Expenditure reducing — fiscal tightening, monetary tightening — lowers the level of absorption.

At less than full employment, switching alone may suffice, because output can rise to meet the redirected demand. At full employment the two must be used together, and this pairing is the reason stabilisation programmes combine a devaluation with fiscal conditions instead of adopting either alone.

The pairing also explains why such programmes are politically difficult. The switching instrument is relatively invisible and its costs are diffuse; the reducing instrument is a decision to cut something specific, and the identity gives no guidance on which.

Saving, investment and the same identity again

The identity has a second form that is worth knowing, because it reframes the deficit as a financing question rather than a trade question.

Absorption is C + I + G. National saving is what is left of income after consumption and government spending: S = Y − C − G. Substituting into the current account identity gives

(X − M) = S − I

The current account equals national saving minus domestic investment. A deficit means the country invests more than it saves and must borrow the difference from abroad; a surplus means the reverse.

This is the same accounting relationship written differently, and it changes the conversation. A deficit read through the trade form invites questions about competitiveness and exchange rates. Read through the saving-investment form it invites questions about why saving is low or investment high, which are frequently the more useful questions.

It also clarifies when a deficit is benign. A country borrowing from abroad to fund productive investment is doing something ordinary and potentially sound; one borrowing to fund consumption is not, and the trade figures look identical in both cases.

Limitations

It is an identity, not a theory. Y − A equals the current account by definition, so the framework cannot say what causes what. It constrains explanations without supplying one.

The channels are weak. As above, the direct effects of devaluation on absorption are several and offsetting, which is why the approach ended as a constraint on policy rather than as a model of adjustment.

It is silent on capital flows. Written when current account imbalances were financed with reserves, it says nothing about an economy whose deficit is financed by capital inflow at an unchanged exchange rate — which is the normal condition of most open economies now.

Distribution is invisible. Reducing absorption at full employment means cutting consumption, investment or government spending, and the identity has nothing to say about which, though the choice is the entire political content of the decision.