IB Economics SL & HLTopic 2.7 — Government InterventionPaper 1 & 2Core idea~9 min read
Why Governments Intervene in Markets
Left alone, a market decides what gets made, how much of it, and who ends up with it — and most of the time it does a decent job. But “most of the time” is not “always”. This page is about the moments when a government looks at a market and decides it cannot leave it alone.
📚 What you need to know
In a free market the price mechanism allocates scarce resources: prices signal, prices give incentives, prices ration.
Almost every real country is a mixed economy — markets do most of the work, government steps in where markets fall short.
There are five common reasons to intervene: correct market failure, raise revenue, promote equity, support firms, support poorer households.
Market failure means the free market allocates resources in a way society would not choose.
The four tools you meet first are indirect taxes, subsidies, price ceilings and price floors.
Every intervention costs something. There is always an opportunity cost, and interventions can misfire.
What a free market does on its own
Start with what happens when nobody interferes. Buyers want the good and firms want profit. The two sides meet at a price, and that price does three jobs at once.
It signals. A rising price tells firms “people want more of this here”.
It gives an incentive. A higher price makes it worth a firm’s while to actually produce more.
It rations. At any price, only the people willing to pay it get the good. Everyone else drops out.
Because of those three jobs, a market pushes itself towards equilibrium without anyone being in charge. If the price sits too high, firms bring more to the market than buyers will take, and the unsold stock forces the price down. If the price sits too low, buyers want more than firms are willing to supply, and the queue pushes the price up. The market settles where the two amounts match.
Notice that the market fixes a wrong price by itself. That is exactly why governments do not need to set prices in most markets.
If a market self-corrects this neatly, your first question in any intervention essay should be: what is stopping it here? Answer that and the rest of the essay writes itself.
So why step in at all?
Five reasons come up again and again. Learn them as a list, because a Paper 1 question that starts “explain why governments intervene” is really asking you to pick two or three of these and develop them properly.
Reason
What it means
Typical policy
Correct market failure
The market is producing too much or too little of something once you count the effects on everyone else, not just buyer and seller
Tax on petrol, subsidy for solar panels
Earn revenue
Governments need money to pay for schools, roads and hospitals
VAT, excise duty on alcohol, sale of licences
Promote equity
Narrow the gap between rich and poor, or make sure everyone can reach an essential service
Minimum wage, free healthcare, progressive tax
Support firms
Keep key domestic industries alive against foreign competition
Subsidies, tax breaks, tariffs
Support poorer households
Reduce poverty and its knock-on costs on the whole economy
Welfare payments, food price ceilings
Equity is not the same as equality. Equality means everyone gets the same. Equity means the outcome is fair — and what counts as fair is a value judgement, so it is a normative idea. That word alone earns marks in an evaluation paragraph.
The four tools you meet first
Two of the tools work by shifting a curve. Two work by drawing a line the market is not allowed to cross. Getting that distinction straight now will save you a lot of confusion later.
Sketch these four rough shapes on scrap paper before an exam. If you can draw all four from memory in 60 seconds, most of 2.7 is already safe.
The idea behind every intervention
free market outcome is not the outcome society wants → government changes prices, quantities or rules
Intervention is never free
This is where most students lose evaluation marks. They explain a policy beautifully and then stop, as if the policy simply works. It never simply works. Three things are always worth saying.
🧩 Three evaluation points that fit almost any policy
Opportunity cost. Money spent on a subsidy is money not spent on something else. Ask what was given up.
How effective is it, really? A tax on a good with inelastic demand barely changes the quantity bought. It mainly raises revenue.
Who wins and who loses? Producers, consumers, workers, taxpayers, the government, the environment. Name at least two.
There is also a bigger worry called government failure: the intervention makes things worse than the problem it was fixing. A price cap that causes a black market, a subsidy that keeps a lazy firm alive, a tax that pushes production abroad. You do not need a whole essay on it, but one sentence showing you know intervention can backfire lifts an answer.
Examiners are not looking for you to be pro-government or anti-government. They are looking for you to weigh both sides and then say which way you lean, and why.
Worked examples
WORKED EXAMPLE
A market that fixes itself
At a price of $50, fans want 12,000 concert tickets but only 8,000 are on sale. At $70, fans want 10,000 and 10,000 are on sale. Explain what the price mechanism does here. [3]
Step 1: Find the gap at $5012,000 − 8,000 = 4,000 tickets of excess demandexcess demand is just the proper name for a shortageStep 2: Say what the shortage does to price
Buyers compete for a limited number of tickets, so sellers can raise the price.
Step 3: Say what the higher price does to both sides
Higher price rations demand down (12,000 → 10,000) and gives sellers an incentive to supply more (8,000 → 10,000).
Equilibrium at $70 and 10,000 ticketsno government needed — this is the market working, not failing
WORKED EXAMPLE
Revenue versus behaviour
A country sells 250 million litres of petrol a year. The government adds a tax of $0.40 per litre, which cuts sales by 5%. Calculate the tax revenue, and comment. [4]
Step 1: New quantity after the 5% fall250,000,000 × 0.95 = 237,500,000 litresStep 2: Revenue = tax per unit × quantity sold237,500,000 × $0.40 = $95,000,000Tax revenue = $95 millionStep 3: Comment
Demand only fell 5%, so the tax is a strong revenue raiser but a weak way of cutting petrol use.
petrol has inelastic demand — people still have to drive to work
WORKED EXAMPLE
Naming the reason for intervention
State the main reason for government intervention in each case. [4]
a) A tax on sugary drinks
Correcting market failure — the market over-consumes a good that harms health.
b) A legal minimum wage
Promoting equity and protecting low-paid workers.
c) A subsidy for a national airline
Supporting a domestic firm against foreign competition.
d) VAT on electronics
Earning government revenue.
many policies do two jobs at once — say the main one first, then add the second
💡 Exam tip
Define market failure early in any 2.7 answer. It is the reason behind most of the other reasons.
When a question says “explain”, one developed reason with an example beats four bare bullet points.
Use the words signalling, incentive and rationing when describing the price mechanism. Examiners look for them.
Say indirect tax, not just “tax”. Indirect means it is paid on spending, and it is collected from producers.
Every evaluation should mention opportunity cost at least once. It is the cheapest mark on the paper.
Learn one real example per reason. A named country or policy turns a generic paragraph into a strong one.
⚠ Common mix-up
“Market failure means the market crashed.” No. It means resources are allocated badly from society’s point of view. The market can be busy and still failing.
Mixing up equity and efficiency. Efficiency is about getting the most out of scarce resources. Equity is about fairness. A policy can improve one and damage the other.
Thinking a shortage means the market has failed. A temporary shortage is the market doing its job. It only becomes a problem when a price control stops the price adjusting.
Assuming government always improves things. Government failure is a real evaluation point and it is badly underused by students.
Calling a subsidy a tax cut. A subsidy is a payment per unit to producers. A tax cut just removes an existing charge.
Up next: Indirect Taxes and Subsidies — the two tools that shift the supply curve, and how to split the burden between the buyer and the seller.
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