(Correction: A previous version of this report used incomplete inventory data in four cities – Charlotte, Modesto, Sacramento and Stockton. Redfin removed those cities while it corrects the data. With 46 instead of 50 markets included in the analysis, the overall share of stale inventory rose from 70.2% to 70.9%.)

Homebuyers are facing a tight housing inventory this spring, and the number of foreclosures available to the typical consumer have shrunk as well.

According to a Redfin report that examined 46 markets to see if fresh inventory is growing, as of March 31, nearly 71% of homes on the market were stale, meaning they had languished unsold for more than a month.

New listings shot up 9.2% last month, but the spring housing bounce is so far nowhere near big enough to satisfy demand.

Nationwide, the total number of unsold homes rose 5.3% in March to 2 million, but at the current pace of sales, that supply would be exhausted in only 4.6 months, according to the National Association of Realtors.

Auction.com Executive Vice President Rick Sharga explained four reasons for why there are fewer foreclosures making it to the market:

1. Lenders are still doing thousands of loan modifications, and in markets where home prices have appreciated over the past few years, like Dallas, those modifications are a little easier to work through, and are often more successful.

2. We're seeing an increase in the number of homes being brought to auctions at Trustee Sales, and at the number of homes being successfully auctioned off at these events to investors. Again, home price appreciation has played a large role in allowing the lenders to sell properties at a price that minimizes their losses.

3. In some high-priced markets, we're seeing a lot of homes (25-33%) sold as "pocket listings." These homes are never published on the local MLS. Agents like these deals, because they typically sell to a buyer they know, and are able to collect both sides of the commission.

4. There's a relatively new program (we're one of the companies involved) where HUD properties are auctioned off more or less immediately they've been repossessed after the Trustee Sale is concluded. These properties typically aren't posted on the MLS either.