Un-advertised Listings Distort Housing Inventory:

The number of homes listed for sale nationally is finally beginning to rise, but ask anyone looking to buy a home and the majority will complain there is nothing out there. Neighborhood to neighborhood, market to market, supply still seems tight, despite a 6.5 percent increase in listings from a year ago, according to the National Association of Realtors. 

"Statistically it appears that we are getting back to very balanced market conditions," said Lawrence Yun, chief economist for the Realtors. "However, the sentiment out there is that we still have a shortage of inventory, and I think that is due to the prevalence of pocket listings in some markets."

A so-called pocket listing is when the real estate agent signs a listing agreement with a seller but does not advertise it widely or put it in a multiple listing service, where other agents and buyers can see it. Instead, they circulate the listing only among their own buyer clients or within their own brokerage. That way they can potentially get commissions on both buyer and seller sides, and would not have to split commissions with other selling agents.

No hard numbers exist on pocket listings so their rise and fall comes anecdotally from Realtors. Pocket listings are not illegal.

The incentive for a seller to do a pocket listing could be that they need to sell the home quickly and don't want to go through a wide marketing plan with multiple showings and open houses. The agent is promising the seller that they know of enough potential buyers personally that they can get a deal done fast. This usually happens when the market is very tight, and buyers are willing to make larger offers up front to negate the risk of a bidding war.