Are jumbo mortgages holding back the housing market?

Yes ... according to the National Association of Realtors in a new report.

While interest rates have gone lower and lower for prime "conventional" mortgages, guaranteed by the FHA, Fannie Mae or Freddie Mac, there is no federal guarantor for the jumbo mortgage market.

According to the NAR, "the national share of home sales above $750,000 has fallen from 4.4% in 2007 to approximately 2.3% in 2009, and the months' supply of inventory has risen from 18.7 months to 41.1 months during that same period."

In other words, it will take more than three years to sell off all the homes that are priced above $750,000 at the current rate. At the same time, the $8,000 first-time home buyer credit isn't going to do you a lot of good when you have to come up with $100,000+ or more just for the 20% down payment.

States that have the highest percentage of jumbo mortgages include Hawaii (43% of all loans are above $417,000), California (41%), the District of Columbia (30%) and New York (22%).