Now that we have more detail, Labour’s new ‘rent control’ policy is not quite as bad as I’d initially feared. Instead of the old school price ceilings that destroyed parts of New York City, Labour are proposing ‘second-generation rent controls’, which limit the ability of landlords to renegotiate rents during tenancies, and ‘make three-year tenancies the norm’.

The real-world effects of this are likely to be that expected rent increases over the three-year lease will be priced in to the starting rent, so it’s unlikely to actually make anyone better off unless there’s an unexpected increase in rents. If rents fall below expectations, this would hurt tenants.

Since landlords are bound within tenancy agreements, rises in rents are likely to be sharper than they currently are for new tenants. This means that housing mobility is likely to be reduced – tenants locked in to a relatively low rent will find it more costly than they otherwise would to move. This is very important: it looks as if lowered housing mobility causes higher unemployment, because people are less able to move to find new jobs.

Rent controls of any kind are likely to decrease the supply and quality of available housing. ‘Second-generation’ controls are less tight and so less harmful than classical rent controls, but as Hopi Sen has pointed out, the German experience does not seem encouraging. There, rents have risen far more quickly over the past decade than they have in Britain, as new construction has slowed.

There is also evidence to suggest that second-generation rent controls have a similarly negative impact on housing quality as classical rent controls. A 1985 study by the Richmond Fed found that controlled housing units were 7.1% lower in quality in 1974, and 13.5% lower in 1977, pointing to a cumulative negative effect. If classical rent controls are only worse than bombing, second-generation controls may be close to petty vandalism.

One interesting aspect of this announcement is that it may affect supply now, as would-be investors in new housing are discouraged by the prospect of stricter controls on their investment. If the measures are actually brought in – crossing the rent control Rubicon – an expectation of tighter controls may reduce supply even more.

It’s not clear what mechanism Labour is proposing to make three-year tenancies ‘the norm’, but it’s hard to imagine any effective measure that would not end up hurting tenants who want shorter leases. This probably means young people.

As we say virtually every day, the best way to reduce the cost of housing is to build more. Labour’s proposals seem counter-productive, but they’re nothing compared to the harm caused by the planning system.

We recently learned that more of Surrey is covered by golf courses than by houses. Rolling the green belt out even a bit – by, say, a mile outside London – would create space for hundreds of thousands of new homes, relieving pressure on existing housing stock, reducing rents and – a nice bonus – creating lots of jobs and adding a few percentage points on to GDP growth. We can dream.