There's one reaction to Nick Clegg's proposal to give free school meals to all young children that is both wrong, and reflective of a wider error.

I'm referring to the notion that it is somehow unfair for the rich to get a benefit as well as the poor. For example, Isabel Hardman says the policy means "giving a £400 annual saving to mothers who are perfectly capable of sending their children to school with smoked salmon sandwiches in their packed lunches." Iain Martin says its "strange" that a benefit should be given to kids "regardless of their parents income." And the IoD says "You need to focus on the people who really need help."

The general error here, of which these reactions are specific examples, is the belief that we should judge the fairness of policies one-by-one. We shouldn't. What matters is the fairness of the overall system, not of individual transactions. As Nick Barr says in the standard textbook on the welfare state:

It is frequently the overall system which is important...Taxation and expenditure should be considered together. (The Economics of the Welfare State, p185, his emphasis)

For example, is it fair that the poor should pay the same rate of VAT as the rich? Is it for that matter fair that they should pay the same prices in Tesco as the rich? Maybe not. But fairness is not the only virtue. Efficiency also matters. Just as it would be absurdly inefficient for Tesco to assess folks' income every time they went to the checkout, so it would be inefficient to means-test all benefits. The inefficiencies take at least two forms. There's the deadweight cost of the bureaucracy required to assess eligibility. And there's the disincentive effects created by those benefits being withdrawn as the individual's income rises.

Given these costs, universal benefits are more efficient. This is especially true for free school meals, which might well have favourable supply-side effects by raising pupils' ability to learn.

If you think such benefits flow too much the wealthy, the solution is not to means-test the benefits themselves, but to tax the rich more. As I say, we should judge fairness at the macro level, not the micro one.

My point here isn't confined to free school meals; it applies equally to child benefit, winter fuel payments and the like. And Ms Hardman is right to point out that Lib Dems attitudes here have hardly been consistent.

Although leftish social democrats have traditionally been most keen upon universal benefits, this should not really be a left-right issue. The left can argue for high universal benefits and high taxes, the right for lower ones - perhaps emphasising the disincentive effects of high benefit withdrawal rates. The only case for supporting means-testing is that you care less about efficiency and more about stigmatizing and vilifying the poor.