One of the topics of the moment is whether or not Congress will bring back the homebuyer tax credit. But this misses the point. The real issue is whether another tax credit would solve the housing crisis in one fell swoop. The short answer is that it wouldn't.

Whether a policy is deemed a success or not depends on what it intends to achieve. If the Obama administration hoped that the first homebuyer tax credit, which ran from January 2009 to April this year, would provide a temporary kick to home sales, then let's break out the ticker tape. Over this period, total home sales increased by 27%, from an annualized 4.9 million to 6.2 million. Of course, not all of these extra sales were due to the tax credit; some homes were brought without the credit while others would have been purchased regardless. Nonetheless, the credit did temporarily boost sales.

But if the aim was to permanently boost demand, thereby closing the yawning gap between low demand and high supply, then the first homebuyer tax credit was a failure. Its greatest feat was to bring sales forward from the summer months to the spring. The result is that in the three months since the credit expired, home sales have plunged by 34%, to 4.1 million.

That doesn't just leave sales below the level seen before the credit was introduced, but it also leaves them at a level not seen in 17 years.

A second tax credit would probably be even less successful. Most households that would like to move and take advantage of the credit have probably already done so. Many more can't take advantage of the credit even if they wanted to. Despite the stronger tone of August's employment report, which was released earlier today, nearly 10% of America's work force is still without a job and another 10% are having to work part-time because they can't find full-time work.

At the same time, according to CoreLogic, the previous sharp falls in house prices have left nearly 25% of all households with a mortgage worth more than their home and half have positive equity of less than 20%. This last point is particularly important as it means half of all homeowners cannot move house or refinance to lower interest payments as they don't qualify for a GSE-backed loan.

The restrictions this imposes are evident within recent data. Even though mortgage rates have plunged to record lows, the number of people applying for a mortgage to buy a home is languishing at a 13-year low. The mortgage bargain of a lifetime is not enough to bring housing demand back to life.

The upshot is that a second homebuyer tax credit would not permanently boost demand by enough to bring it in line with the still high levels of supply. Housing demand is set to remain weak for a number of years, which over the next 18 months will contribute to a renewed fall in prices of between 5% and 10%.