Do newspapers provide a public good that wouldn't exist in their absence? It's that question that should determine our reaction to David Leigh's proposal for a ''2 per month levy on broadband to subsidize newspapers.

There is some evidence to support him. When the Cincinnati Post closed in 2007, voter turnout fell and incumbent councillors were more likely to be re-elected, suggesting that the decline of even small newspapers worsens democracy.

However, I'm not sure this is a clinching argument, for four reasons:

1. The MSM isn't just a public good, but a public bad. The likes of Richard Littlejohn, Rod Liddle and some parts of Comment is Free help to coarsen and devalue political discourse. So too do journalists' sloppy (pdf) thinking and lazy churnalism. It's not obvious why low-paid workers and highly-indebted graduates should be forced to pay more so they can top up Paul Dacre's ''1.7m salary. Granted, local newspapers are more of a public good - but Leigh's proposal won't much help these.

2. Leigh's proposal to subsidize papers "in proportion to their UK online readership" provides an adverse incentive. It would further incentivize cheap linkbaiting rather than expensive investigative journalism.

3. It's not clear that newspapers provide much news or analysis that isn't available elsewhere, most notably on the BBC. In today's Times - to take the example nearest to hand - there seems to be only one exclusive UK story of public concern. In economics, do newspapers really tell you much that you couldn't get from the BBC, the ONS or our better econobloggers?

4.It's possible that if newspapers were to disappear, other forms of journalism - some unforeseeable - would expand to fill the gap. Subsidizing newspapers thus helps keep dinosaurs alive and retards the creative destruction that might give us a healthier journalism.

On balance, then, I don't see much merit in Leigh's idea. The case for subsidizing newspapers is about as strong - and arises from the same motive - as my belief that the government should subsidize left-handed cat-loving guitar-playing economists.