I disagree: if Jane first home buyer has an income of $50000, and can only just afford $30000 per year on their mortgage, Jane will bid on a house the maximum she can afford. I agree that over the long term, with everybody acting the same as Jane, then the price of homes is mostly controlled by the interest rates. However interest rates, per se, do not affect the affordability of homes very much.
There are secondary effects that do change things. However the primary market dynamic of bidding as-much-as-you-can-afford means that affordability doesn’t change much. (It also means your population is playing a zero-sum bidding game of how-much-can-we-pay-the-banks, which is bad, especially in New Zealand which doesn’t own most of its banks).
Secondly, the usual answer is to increase housing supply. That would work only if there can be a super-abundance of new supply in a suburb. Think of a desirable locarion, and let’s magically create 20% more homes there. Would that fix supply? No, because the latent demand is far bigger than 20%. Why? Firstly, in my circles in Christchurch NZ, relatively well-off people own multiple homes: their primary home in the suburbs, sometimes a second home or an investment property (rented or Airbnb), ideally a holiday home somewhere which is often empty, perhaps even a town-house in a city. Secondly, in my other circles there are a lot of people sharing a home (one home split into several flats, flatting, still living with parents), so there is a huge latent demand for people that want their own home.
I think that in many desirable suburbs, you could double the number of homes and prices would not shift down in the slightest. For people to own their own homes needs something new to happen.
We have had a housing boom going on in Christchurch for say 5 years now, and house prices went up and up, because people bid what they can afford. Projections are for housing to increase faster than population in Christchurch, but that is not fixing affordability. Statistics: “Christchurch City's most recent population estimate was 392,000 (June 2021). The 2010/2011 earthquakes resulted in a net loss of around 21,000 people, but by 2017 the city's population had recovered to pre-earthquake levels. Projections suggest that by 2028 the population is likely to be around 417,000 under a medium growth scenario.” “In 2018, there were an estimated 148,000 households in Christchurch city. Projections suggest that this will likely increase to around 161,000 households by 2028 (medium series).” https://ccc.govt.nz/culture-and-community/statistics-and-fac... I don’t understand their projections, because on the same page they show a graph with more than 10000 new homes already. Also we have massive housing growth outside of Christchurch - I have seen recent large subdivisions in: Rolleston, Lincoln, West Melton, Amberley, Methvyn, etcetera.