Plunging rents are great news for renters, but they're lousy news for homeowners. Aaron Task and I discussed this issue on TechTicker this morning:

The vacancy rate for rental apartments in the U.S. is now 7.8% and climbing, says the Wall Street Journal. This is the highest vacancy rate in 23 years.

Worse, the vacancy rate is expected to keep climbing through the winter, ultimately hitting the highest rate on record.

This is good news for renters and bad news for landlords. It's also bad news for anyone who owns and would like to sell a house.

Why are rising rental vacancies bad news for homeowners?

Because rising vacancies put pressure on rents, as landlords have to cut prices to woo a smaller pool of tenants. As rents drop, meanwhile, one of the key measures of house-price value--the price-to-rent ratio--also changes, and not for the good.

All else being equal, when rents drop, the "Housing P/E ratio" -- price to rent -- increases as rents decrease. This is the same thing that would happen to the P/E ratio of a stock if the company's earnings began to shrink.

The more the rent/earnings shrink, the more expensive the house or company is as a multiple of the rent/earnings.

Will people suddenly refuse to pay as much for houses because the price-to-rent ratio rises a bit? No. But they may decide to rent instead of buy, which will remove some demand from the housing market. And, this, in turn, will put pressure on house prices.

The chart below from Calculated Risk illustrates the price-to-rent ratio over the past 15 years. As you can see, it got way out of whack during the peak bubble years and has now fallen back within the realm of normal. As rents fall, however, the ratio will start rising again.

That is, unless house prices fall, too, which is the more likely scenario.

See Also: HOUSING RECOVERY! (How's Your City Doing?)