New house sales were down 5.5 percent in September from their August level and by 13.2 percent from year-ago levels. This is pretty much the textbook story of crowding out from the tax cut.

The story holds that if the government runs large deficits when the economy is near full employment, it will lead to higher interest rates. Higher rates then discourage home buying and construction, investment, and raise the value of the dollar, thereby increasing the trade deficit. These factors together offset the stimulus from the tax cut and eventually leave GDP pretty much the same as it would be without the tax cut, and possibly lower over the long-run.

Of course, it is important to note the role played by the Federal Reserve Board in this story. It has raised repeatedly, partly in response to the boost to growth caused by the tax cut. It has also indicated that it intends to continue to raise rates unless growth slows substantially.

The Fed would justify its rate hikes by claiming the need to prevent a rise in the inflation rate. While this could be right, there is a huge amount of uncertainty about the risk of inflation. To my view, we would be much better off waiting with the rate hikes, and seeing how low the unemployment rate could go, and only begin to raise rates after there is clear evidence of rising inflation. But, I'm not running the Fed.

Anyhow, we are clearly seeing the impact on housing. Mortgage interest rates were just over 3.9 percent last October. Today they are 4.7 percent. This is the main factor weakening the housing market.

And, while the monthly sales data are erratic, we have developed a large backlog of unsold houses, so that the inventory is now equal to 7.1 months of sales. This is the highest inventory since early 2011. This is virtually certain to lead to further declines in construction in the months ahead.