> No, lack of building _is_ the main problem.

This might be one of those things where the obvious bit (built more!) is both true, and reductively incomplete. We do have a sense that just building more housing in the presence of lots of liquid capital and easy credit seems to create a speculator market -- even down to retail investors. (e.g. The China real estate bubble bursting seems to be strong evidence that this can happen.)

We also have some evidence that building a single type of housing leads to another kind of speculator bubble (e.g. the subprime mortgage crisis of the early 2000s was proceeded by a massive wave of construction of primarily giant single family homes for example). Even if somebody was interesting in buying something smaller at that time, there wasn't inventory anyways - yet those smaller housing units were not where prices increased the most (note: I'm aware I'm not providing specific evidence of this, but if memory serves it's basically correct) yet they often saw large increases in rental prices.

So from those two examples we can likely say that a market that:

1. Speculation causes housing prices to rise, even when millions of units are being built.

2. Lack of diversity in housing construction can lead to both high prices for some types of stock and lack of availability for others.

So how can we solve this beyond the trivial "build more"?

I'm starting to believe a few things are needed for a healthier housing market:

* We need to limit housing speculation, or at least make it less interesting as an investment option. In South Korea, they've introduced various taxation schemes that limit the appeal of owning multiple properties after decades of housing speculation. The idea there is that housing does exist, but occupancy rates are lower than desired. The result seems to have been an explosion in new housing starts with entire districts in Seoul being razed and rebuilt.

* We also need to find ways to ensure diversity in housing. Now that interest rates have gone up and single family homes seemed to have softened as a market, it seems that developers are concentrating on building "luxury" units of various other types. It's a good start, but if these units are still outpricing need, then they'll sit empty or end up speculated on. Many areas have dealt with this by mandating a certain amount of "affordable" housing, but that has turned into a joke in these areas.

There needs to be other ways for developers to build lower budget units, perhaps tax incentives, or changing zoning to allow for more types of housing.

Here's an example of the problem: The D.C. Metro recently added an entire new line to the system intended to connect the major international airport into the city. The areas around the new stations along the line have all been subject of new rezoning plans, higher density, urban fabric, etc. However, the construction that's happening along that line, while adding tens of thousands of new housing units, is almost all "luxury" (e.g. high price). One of the areas along the line is among the largest reurbanization projects on the planet (Tysons), and Reston/Herndon could grow into a contiguous "city" as large as many other "name recognized" cities in the U.S. like Providence, or Salt Lake City. Average housing unit prices in that area have been rising double digit percent per year (quarter over quarter) with the average home price (not just single family, but condos, town homes, etc.) is at around $700k USD. People who bought in this region even just a few years ago would be unable to afford their own homes today given pricing and interest rates.

So we see another example of "build more" and even "build more types" but aren't being met with "limit speculation" and "build more diversity" - and even in the presence of harder to get credit, the prices are spiraling.