@Matt Garboden, the concern for rent affordability is valid. If the response to the concern is pointing fingers, we have a problem and not a solution. The ability for the largest land owners to absorb costs does not prove other landlords are price-gauging jerks. The responsibility to provide affordable housing is not the responsibility of a single group.
In my view, there are conditions in the Portland real estate market that are beyond the control of most landlords. Landlords did not set federal interest rates which have been at historic lows causing increases in prices. Landlords did not (well maybe some) make Portland a desirable place to live and work. For many landlords, who we call moms and pops, the controls proposed are too onerous.
I disagree that any U.S. real estate market is a free market. There are hundreds of regulations from the local level up to the federal level directing real estate market participants. Landlords cannot discriminate against protected classes of individuals. Landlords cannot rent dangerous units. Nor should they.
The fact that landlords and tenants respond to market factors does not make the Portland market free or efficient. I agree with you, @Matt Garboden, if rents or cap rates aren't good, if investments don't pencil out, investors will not invest. But that's the problem if you take a market approach. It doesn't necessarily follow that prices will fall. Demand would have to be constant (stagnant) for supply shifts to explain 100% of market price. Rental affordability (price) is not solely a factor of supply or demand. It's a combination.
A VERY unpopular opinion I enjoyed is this: Much of Portland should be down-zoned. This view assumes sales prices are high because everyone thinks their property will be the next higher-density development. They want the big payout the last guy or gal got. So everyone holds out. The problem of hold outs is well studied and I think it explains some of the pricing and affordability problems in Portland.
I also believe demand partially explains Portland's high rents and prices. I don't believe setting a price ceiling or imposing taxes on supply will give us more affordable housing. We need more units constructed to catch up with demand, not fewer. Portland should be doing everything it can to attract real estate developers to increase housing supply to reduce rents. Right now, the new buildings coming online have ridiculous prices, more competition, in the market theory, is the right response. How this ought be done is another story.