As reports of inventory shortages keep appearing, the driver isn't entirely that investors are crowding out retail home purchasers -- as Trulia (TRLA) chief economist Jed Kolko notes in an article appearing at The Atlantic, vacancy rates are unusually high. Homes are intentionally being kept off the market:

But wait – aren't homes hard to find? Buyers (and renters, too) have had little to choose from because the listed inventory is low. The share of the overall housing stock that is listed for sale, based on National Association of Realtors and Census data, rose slightly in 2013 Q3 compared to last year but is lower than at any other point during or after the bubble. In other words, the for-sale inventory is back down to its 2000 level, and tight inventory has helped fuel sharp price increases across the country over the past two years. That means there’s an inventory shortage, but not a housing shortage.

Kolko also takes a look at where the vacant inventory is clustered in the US, and finds some interesting trends:

The vacancy rate is higher today than it was before the bubble in 86 of the 100 largest metros. That means that the elevated vacancy rate at the national level is widespread at the metro level, too.