This is not an abstraction: buildings large and small are showing gaping vacancies. Storefronts are empty. Entire buildings sit waiting to be occupied. In Manhattan, retail vacancies have reached their highest rates since 2001. For the second quarter of this year, vacancies hit the absurd height of 12.4%, thanks to unemployment trends that won't quit and consumers reluctant to pry open their wallets.

Retailers are being hit just like the residential market.

Apartment vacancies in the United States hit their highest level in 22 years in the second quarter of 2009. Job losses are to blame, according to Bloomberg, as tenant demand falls when people don't have any income. Vacancies rose to 7.5% from 6.1% year-over-year, according to Reis Inc. But this still doesn't reach the 1987 level of 7.6%. In June, the U.S. unemployment rate hit a 26-year high, with payrolls dropping faster than expectations.

Conventional wisdom has it that potential homebuyers turn into renters when the job market softens. The rental pool is shrinking, however, leading to the high rate of apartment vacancies as landlords struggle to fill units. Asking rents for apartments fell 0.6% last quarter (for the second in a row), according to Reis, the largest fall since the company started to track this measure in 1999. Overall, asking rents (including other types of residences) were off 0.7% year-over-year, down to an average of $1,040 a month.

Is now a good time to buy a home? Obviously that depends on where you live, but there's so much conflicting information out there. Straight-up predictions of home price fluctuations have their limitations, but looking at rental-related statistics like vacancies and the growth rate in rental prices can tell you a lot about the health of a market. Real estate services company and investment firm Grubb & Ellis Co. released its predictions for the 2009 real estate market. On the housing side, the company anticipates that an increasing supply of unsold condos and homes being made available for rent may cause an increase in vacancy rates.

Here's the company's list of the ten best rental markets for 2009-13:

• Los Angeles
• San Francisco
• Orange County, Calif.
• Oakland/East Bay, Calif.
• Washington, D.C.
• San Diego
• New York City
• San Jose, Calif.
• Long Island, N.Y.
• Portland, Ore.

It's good to be skeptical of predictions, but some of the names on the list are quite interesting. High foreclosure rates in Los Angeles and other cities have sent property values plunging, and that might provide good opportunities for long-term investors.