What is the cause of house price inflation?

[Spoke]

@Maastricht

In the Netherlands another phenomenon explains housing prices: “woonverdunning” which translates roughly as housing dilution.

The number of individuals sharing an house or apartment had decreased over the last decades, so that more and more houses are needed even while the population does not increase that hard.

Something analogous has happened in the US over the past decade with explosive growth in the ownership of second homes. Is that sustainable? I dunno.