On HN and on tech twitter I often see this statement: “the reason rents are high is because we don’t build enough houses.”
But I don’t think that’s really true, I think that’s very simplistic. The missing observation is that housing has become an asset class in a way it wasn’t in the past. Large numbers of people purchase houses to rent seek as landlords, and the only limit to the demand for rent seeking is the ability of those landlords to borrow money. So a major determinant of rent is now the ability to borrow money, the interest rate, and the number of people wanting to be rent seeking landlords.
Increasing the housing supply by the amount physically practical in say the course of a decade is probably unlikely to make much difference to rents if the primary driver of rent prices is the ability of rent seekers to borrow to buy the new properties. First time buyers can’t compete on borrowing because they have smaller deposits or less access to capital, so they are forced to rent, which means the rent seekers can continue to buy up properties.
In the UK, buy to let mortgages have become a substitute for pensions for the baby boomer generation. Encouraged by the government, housing as a yielding asset has essentially taxed the young to pay for the boomers retirement.
Whilst housing can be used as a rent seeking asset, it is very unlikely building new houses is going to lower rents. Landlords will simply always be able to outbid renters, so rent will remain at the height of whatever the renters can afford, I.e. extract the maximum rent possible. There is an endless demand for housing from rent seekers, provided they can rent out that property.
Couple this with the fact that the government in the UK at least has used the property market to hide the reality of the economy - that the economy is basically collapsing - there is so much vested interest in maintaining the status quo that no regulation will be introduced that will cause rents to drop, such as limiting the access of rent seekers to capital, or preserving properties for owner buyers etc.
Tl;dr - rents are expensive not because there is too little housing, but because we need them to be expensive.