By testing each case rather than applying a single rule — because this chapter shows the same tool producing opposite results in different markets. A useful way to answer is to set out the tests a government could apply, drawing on the two sides the chapter itself lays out.
| Test | The question to ask | Where the chapter shows it |
|---|---|---|
| Is the market failing? | Is an essential good beyond people's reach, is a public good going unprovided, or does a monopoly control supply? | The three reasons the chapter gives for intervention |
| Who is being harmed? | Are “vulnerable and low-income groups” being priced out, or are workers being paid too little? | Fairness and equity in allocation, page 206 |
| Is the remedy proportionate? | Would a lighter measure work — better information, a complaint body, more competition — before fixing a price? | Regulators such as CCPA and TRAI ensure transparency without setting prices |
| What does it cost the other side? | Will producers stop supplying, will small firms drown in compliance, will innovation stop? | The three limitations on page 208 |
| Is it reviewed? | Is the measure re-examined once the emergency passes, using evidence of what it actually did? | The sanitiser cap was an emergency measure, and the box asks whether such controls should last forever |
And ‘how much’ follows from ‘when’. The chapter's own examples suggest a ladder: first make the market work honestly (regulate unfair practices, ensure transparency); then, if that is not enough, act on quantity and access (provide the good publicly, encourage new sellers to enter); and only where people would be harmed in the meantime, act directly on price with a ceiling or a floor. The heaviest tool is used last and reviewed first.