How Low Aggregate Demand Damages the Supply Side, and Demand-Management vs Supply-Side Policy for Recovery

Answer

Part (a)

A sustained period of low aggregate demand damages the supply side because the prolonged slump erodes both the quantity and the quality of an economy’s productive resources, contracting short-run aggregate supply (SRAS) and long-run aggregate supply (LRAS).

Investment collapse and capital decay. Persistently weak AD signals a poor profit outlook, so the marginal efficiency of investment falls and firms cut investment expenditure. A prolonged recession also shrinks the lending capacity of the financial system — banks, facing higher default risk, ration credit and raise the cost of borrowing — which depresses investment further. Because gross investment falls below the rate of capital depreciation, the economy’s capital stock contracts. With fewer machines and less infrastructure per worker, the economy’s productive capacity falls, shifting LRAS leftward.

Labour-force withdrawal and skills erosion. When demand stays low for an extended period, demand-deficient unemployment is sustained. Discouraged workers, unable to find jobs, leave the labour force entirely, reducing the quantity of labour available. Those who remain unemployed see their skills atrophy, lowering labour productivity — a hysteresis effect in which a temporary demand shock leaves a permanent supply scar. The fall in both the quantity and quality of labour shifts LRAS leftward.

Higher unit costs and cost-push pressure. The contraction in the supply of loanable funds and of labour raises the prices of these inputs — higher interest rates and, where labour is scarce in particular sectors, higher wage costs. Rising unit costs of production shift SRAS leftward, generating cost-push inflation. The leftward shift of LRAS and SRAS together means the economy can produce less at every price level, with a lower potential output and a higher general price level — precisely the stagflationary combination of recession and cost-push inflation described in the preamble.

In sum, a sustained period of low AD damages the supply side by running down the capital stock, shrinking and de-skilling the labour force, and raising unit costs — contracting both SRAS and LRAS.

Part (b)

The pandemic has left two distinct problems: deficient demand (recession, demand-deficient unemployment) and a damaged supply side (lost capacity, cost-push inflation). My thesis is that neither family of policy is universally superior: demand-management addresses the demand shortfall directly and quickly, but supply-side policy is the only instrument that repairs the structural damage and tackles cost-push inflation. Effectiveness depends on the root cause being targeted, the size of the multiplier, and the time horizon — and the strongest recovery pairs the two.

Demand-management raises AD and closes the output gap. Expansionary monetary policy — lower interest rates — reduces the cost of borrowing, raising firms’ investment and lowering the opportunity cost of consumption, so $C$ and $I$ rise. A weaker exchange rate (where the central bank manages the currency) makes exports cheaper and imports dearer, raising net exports provided the Marshall-Lerner condition holds. Expansionary fiscal policy — higher government spending on infrastructure and digital connectivity — raises $G$ directly. Through the multiplier, the rise in AD produces a more-than-proportionate rise in national income.

Limitations of demand-management. During a pandemic, pervasive risk and uncertainty blunt the interest-rate channel: firms and households may refuse to borrow even at low rates, so monetary policy “pushes on a string”. Exchange-rate depreciation is double-edged for an import-reliant economy such as Singapore — it imports cost-push inflation, worsening the very supply-side problem the preamble describes. Fiscal expansion requires fiscal space; an indebted government that must borrow from the public may crowd out private spending. Crucially, demand-management does nothing for the damaged supply side: raising AD against a leftward-shifted AS aggravates cost-push inflation rather than relieving it.

Supply-side policy repairs capacity and lowers costs. Supply-side policies such as reskilling and upskilling (Singapore’s SkillsFuture) raise labour productivity and re-attach discouraged workers to employment. Higher productivity lowers firms’ unit costs, shifting SRAS rightward and easing cost-push inflation, while the expansion of the economy’s productive capacity shifts LRAS rightward.

Limitations of supply-side policy. Its effects are slow — reskilling bears fruit only after a long time lag, so it cannot close a recessionary gap quickly. It also depends on workers being receptive: a rational worker reskills only if the private benefit exceeds the private cost, so take-up may be low without sufficient subsidy.

Judgement. Which is more effective turns on the root cause, the size of the multiplier, and the time horizon. For an economy like Singapore — small, open, with a high marginal propensity to import and to save and hence a small multiplier — demand-management is comparatively weak: an injection leaks abroad rather than circulating, so AD-based recovery is muted, and a weaker currency risks cost-push inflation. Supply-side policy is better matched to the pandemic’s actual damage, since it simultaneously raises real output and relieves cost-push inflation. Yet supply-side policy is too slow to address the immediate demand collapse. The reasoned position is therefore sequencing rather than choosing: demand-management to arrest the immediate downturn and prevent further hysteresis, with supply-side policy as the durable instrument that repairs capacity and addresses the cost-push inflation that demand-management alone would worsen. Used together, and calibrated to a small-multiplier, import-reliant economy, they are more effective than either alone.