Recently the driver of a bus refused to let me on unless my baby buggy was folded up. He then sped on, leaving me stranded. It would have taken only a moment to fold up the buggy. Is this efficient?

Mary McLaren,

Hackney, London

Dear Ms McLaren,

I'm sorry to hear of your distressing experience but the driver did the right thing. You say it would have taken a moment to fold up the buggy. My generous estimate is that you would have delayed the bus by at least 30 seconds. London buses seat up to 75, plus those standing. Let us be conservative and say that there were only 40 passengers on it. By waiting for you to board with your baby and buggy, the bus would have delayed 40 people for 30 seconds, an aggregate delay of 20 minutes.

You and your baby should have picked up the next bus in 'about six to 10 minutes, so the aggregate delay there is around 16 minutes. Sixteen minutes is less than 20 minutes, so the driver maximized social welfare by refusing to wait.

Of course, not every political philosopher accepts the tools of cost-benefit analysis. The two modern greats, John Rawls and Robert Nozick, have different views.

Rawls is concerned with the welfare of the worst-off in society: you, standing at the bus stop rather than the happy multitude already on the bus. Rawls presumably believes no delay is too great to allow you to get your baby on the bus.

Nozick, on the other hand, would say that the rules were clear and you did not follow them. Regrettable as your self-inflicted plight was, perhaps you will be more considerate of other passengers in future.

Tim Harford

Dear Economist columnist

Resolving readers’ dilemmas with the tools of Adam Smith