1The idea in one paragraph

Demand-side policy changes how much the country spends. Supply-side policy changes how much the country can make. Supply-side policies are government policies aimed at increasing the quantity or the quality of factors of production, and at improving the efficiency with which they are used, so that the economy's productive capacity — the most it can produce when its factors are fully employed — goes up. On the diagram that means shifting the LRAS curve, or the Keynesian AS curve, to the right. If it works, the country ends up with more output at a lower price level, which no demand-side policy can deliver. The catch is in the words "if" and "ends up": these policies are slow, expensive in one way or another, and never certain.

2What supply-side policies are trying to do

The guide lists five goals. They are five ways of describing the same shift of the AS curve, and Figure 1 shows how they join up.

Long-term growth by increasing productive capacity. Growth that comes from a bigger capacity, not from spending more of an existing capacity.

Improving competition and efficiency. The same factories and the same workers produce more, because resources move to the firms that use them best.

Reducing labour costs and unemployment through labour market flexibility. Labour market flexibility means wages and working arrangements that adjust quickly to conditions. Cheaper and more adaptable labour is meant to make firms willing to hire.

Reducing inflation to improve international competitiveness. Lower costs mean lower prices; lower prices at home than abroad mean exports sell better.

Increasing firms' incentives to invest in innovation by reducing costs. A firm that keeps more of each pound of profit has more reason to spend on new equipment and new ideas.

3What success looks like, in both models

Draw the outcome before you argue about the policy. Figure 2 does it in the monetarist/new classical model, where the LRAS curve is vertical at potential output.

Capacity rises, so LRAS moves from LRAS₁ to LRAS₂, and the same improvement that raised capacity also lowered firms' costs, so SRAS moves right with it. Aggregate demand has not moved at all. Output rises from Y₁ to Y₂ and the price level falls from P₁ to P₂. That combination — more output, lower prices — is the entire case for supply-side policy, and you should say it in those words.

The Keynesian AS curve gives the same answer only sometimes, which is why Figure 3 has two panels.

In the left panel the economy is on the rising section of the AS curve, near capacity, and the result matches Figure 2: output up, price level down. In the right panel the economy sits deep in the flat section, with idle factories and unemployed workers. Building more capacity there changes nothing. Output is decided by how much people are buying, not by how much the country could make, so Y and P stay exactly where they were. A Keynesian economist draws the right-hand panel and says: fix demand first.

Supply-side policy moves the AS curve, so if it works you get more output at a lower price level. Demand-side policy moves AD, so more output comes at a higher price level. The difference in the diagram is the difference in the argument.

4Two families, and never blur them

The guide splits supply-side policies into two groups, and marks them separately. Market-based policies work by removing obstacles so that markets, prices and competition do the work: the government does less. Interventionist policies work by the government spending money and directing resources: the government does more. Figure 4 is the sorting board.

Two traps. Anti-monopoly regulation is a market-based policy even though it is a regulation, because its purpose is to make a market more competitive rather than to have the state produce something. And education and training are interventionist even when the aim is a more flexible workforce, because the taxpayer pays for them. Sort the policy into a column before you write a word about it.

5Market-based: policies to encourage competition

Four policies, one argument. Deregulation removes rules that restrict entry or raise costs, such as a licence needed to run a bus route. Privatisation transfers a state-owned firm into private ownership, on the argument that private owners face a profit incentive and competitors. Trade liberalisation lowers tariffs and quotas, so domestic firms must match foreign rivals and can buy imported inputs more cheaply. Anti-monopoly regulation stops a dominant firm abusing its market power, blocks a merger, or breaks a monopoly up.

Follow the chain in Figure 5 with Verland, our example economy. Verland deregulates intercity coach routes, which had needed a licence. Four new operators enter, fares fall by 15%, and the old operator cuts the empty mid-week services it had been running. Costs fall across every industry that moves goods and people, so SRAS shifts right; resources move from a protected firm to better users, so LRAS shifts right too.

The case for. Better resource allocation, and almost no bill for the government: the coach reform cost Verland a change in the law. Privatisation raises money rather than spending it.

The case against. The licence may have been doing a job — vehicle safety checks, or a rural route nobody will run for profit. The old operator's staff lose work this year, while the gains arrive over several. And trade liberalisation costs the government its tariff revenue.

What it depends on. Whether the market becomes genuinely competitive. Selling a state monopoly to a private owner who is still a monopoly changes who collects the profit, not how efficiently the industry runs.

6Market-based: labour market policies

The aim is labour market flexibility, and there are three named policies. Reducing the power of labour unions — narrowing the right to strike, or limiting collective bargaining to a single firm — is meant to slow wage growth and make firms readier to hire. Reducing unemployment benefits raises the gap between benefits and pay, so that taking a job pays more clearly. Abolishing minimum wages removes a legal wage floor. Figure 6 is the diagram the guide names, and you must be able to draw it.

Verland's minimum wage is V9.00 an hour and the market-clearing wage in the left panel is V7.50. At V9.00, firms want Qᴅ workers and Qs want work, so the shaded gap is an excess supply of labour, which is unemployment. Abolish the floor and the wage falls to V7.50: employment rises to Qᴇ, and the people who were already working lose V1.50 an hour.

The case for. More people in work, lower labour costs, and firms that can adjust hours when demand changes.

The case against. The cost falls on people at the bottom of the pay distribution, immediately and by a known amount, while the promised jobs are a forecast. Weaker unions and lower benefits do the same thing: they lower the incomes of the people with least. This is the equity issue the guide names, and it is a genuine disagreement, not a settled question. One economist reads the diagram as unemployment removed; another says a wage floor is what stops employers with local market power paying less than the work is worth, and that the diagram assumes the competitive labour market it is trying to prove.

What it depends on. How competitive the labour market really is, how far the minimum wage sits above the market-clearing wage, and whether the people who lose the V1.50 are compensated some other way.

7Market-based: incentive-related policies

Two policies here: personal income tax cuts, and cuts in business tax and capital gains tax (a capital gains tax is charged on the profit made when an asset is sold). The reasoning is about incentives. Keep more of what an extra hour earns and you may work more hours; keep more of a firm's profit and investing that profit becomes worth more; keep more of a gain on an asset and putting money into a business beats leaving it in a bank.

Figure 7 shows why the chain is not automatic. Verland cuts its basic income tax rate from 30% to 24%. For some workers the substitution effect dominates: an hour of work now buys more, so they work longer. For others the income effect dominates: the same hours now cover the bills, so they work less. Which effect is bigger is a question about evidence, and it differs between countries and between groups of workers.

The case for. Stronger incentives to work, to invest and to innovate; and, supporters argue, a wider tax base that eventually returns some of the lost revenue.

The case against. The revenue goes immediately. Verland's cut costs V6bn a year from the first year, which must come from borrowing or from spending cuts, and either has its own cost. The gains from an income tax cut are largest for people who earn most, and a capital gains tax cut goes only to people who own assets, so the distribution of income widens unless something else offsets it. Against that, a bigger economy can fund more services later, and jobs created by new investment go to people who had none.

What it depends on. Whether the incentive response is large enough to be worth the revenue, and how a government fills the hole in the meantime.

8Interventionist policies

Here the government pays. Education and training raise the quality of labour — human capital. Improving the quality, quantity and access to health care keeps workers healthy, at work, and working for more years. Research and development funding pays for the basic research that no single firm can capture the returns from. Provision of infrastructure — ports, rail, power, broadband — lowers costs for every firm that uses it. Industrial policies are targeted support for sectors judged important for future growth: grants, tax breaks, cheap credit or public procurement aimed at one industry.

Figure 8 puts Verland's programme on a timeline: a V2.1bn port berth that takes six years to build and lifts capacity from year seven, retraining at V400m a year that shows up from year three, school reform that reaches the workforce in year eleven, and R&D grants that may produce nothing at all.

The case for. Direct support of sectors that matter for growth, and provision of things markets underprovide because the benefits leak to everyone: basic research, a port, a healthy population. A government can also aim the money at a region that markets have left behind, which is why interventionist policy is often defended on equity grounds as well as efficiency ones.

The case against. The cost. Every V in Figure 8 is raised in tax or borrowed, and it buys nothing else for that decade. The government also has to pick correctly: an industrial policy is a bet by officials on which sector will matter in fifteen years, and if the bet is wrong the money is gone. Firms with good lobbyists are better at getting the grant than firms with good ideas.

What it depends on. Whether the state can identify the gap the market left, and whether the country can carry the cost while it waits.

9The two side-effects the guide names

Demand-side effects of supply-side policies. Almost every supply-side policy also moves AD, usually before it moves AS. Figure 9 follows Verland's income tax cut.

In year one, households have more disposable income, consumption rises, and AD shifts from AD₁ to AD₂. Capacity has not changed, so the economy is pushed past LRAS: output rises to Y₂ and the price level rises to P₂ — an inflationary gap, the opposite of goal four. In year ten, if the incentives worked, LRAS and SRAS shift right too and the price level comes back down to P₃. Everything between those two panels is the risk. The same is true in reverse for a benefit cut, which lowers the incomes of households that spend nearly all of what they receive, so AD shifts left while the supply-side effect is still years away.

Supply-side effects of fiscal policies. The link runs the other way as well. Fiscal policy is demand management, but what a budget is spent on decides how much capacity the country has later.

In Figure 10, all three parts of Verland's V180bn budget move AD this year. Only some of it moves AS later: capital expenditure on ports, laboratories and schools, and the part of current expenditure that pays teachers and nurses. A rise in pensions supports demand but adds nothing to capacity. So a government choosing between a pension rise and a port is choosing between output now and output later, and an exam answer that says which is doing real analysis.

10Supply-side against demand-side

This comparison is the most common part (b) in the unit, so learn it as a pair of diagrams rather than as a list.

Both panels of Figure 11 raise output by the same amount. The demand-side panel — monetary policy from 3.5, fiscal policy from 3.6 — shifts AD right and pushes output past LRAS, and the price level rises from P₁ to P₂. It works within months. The supply-side panel shifts SRAS and LRAS right with AD untouched: the same extra output arrives with the price level falling to P₂, but it arrives in about ten years, and only if the policy did what it promised.

Two conclusions worth writing. Demand-side policy can raise output above capacity for a while, but only supply-side policy raises capacity itself, so long-run growth has to come from 3.7. And a country in a deep recession cannot wait: the right-hand panel of Figure 3 is exactly the case where supply-side policy alone leaves output where it was. They are complements, not rivals — demand-side for the cycle, supply-side for the capacity.

11How well do they work?

An evaluation question wants the strengths, the constraints, and a judgement about the objective in the question. The guide's own lists:

Three of those need care. "No burden on the government budget" is clearest for deregulation, anti-monopoly regulation and privatisation, which cost the state almost nothing and can raise money; tax cuts are market-based too, and they do lose revenue from day one, so name which policy you mean. Vested interests are the groups who lose from a reform and are organised enough to stop it: the licence holders in Figure 5, a union facing weaker bargaining rights, the managers of a firm about to be sold. Environmental impact is a real constraint on deregulation, because some of the rules being removed are the ones protecting air, water or land.

Now the three objectives.

Economic growth. Supply-side policy is the only kind that raises potential output, so it is the strongest of the three claims. The limitation is time: nothing in Figure 8 helps this year's growth figure, and a government facing an election in two years has weak reasons to start it.

Low unemployment. Good at the kind of unemployment that comes from workers lacking the right skills or living in the wrong place, because retraining and infrastructure attack exactly that. Weak against unemployment caused by a fall in demand, which needs 3.5 or 3.6. If the question describes a recession, say so.

Low and stable rate of inflation. The attractive claim: lower costs and more capacity reduce inflationary pressure without cutting output, which is what makes supply-side policy different from raising interest rates. The limitation is that it is far too slow to answer an inflation problem this year, and, as Figure 9 shows, the demand-side effect can raise inflation first.

The honest summary, and a good final paragraph in an essay: supply-side policies are the only tools that raise what a country can produce, but they work slowly, their size is uncertain, and each one sends a bill to somebody — the taxpayer for the interventionist ones, and usually people on lower incomes for the market-based labour market ones.