As demand for single-family houses begins to weaken, supply is starting to leap. After the 2008 financial crisis wiped out many homebuilders, the survivors were extremely cautious. But with the passage of time, their confidence has leaped. From an index low of 9 in 2009, it climbed to 76 in December 2019 just before the pandemic, and in January of this year, rose further to 83, well above the pre-financial crisis top of 72 in June 2005. The number of new houses under construction exceeds completions by the largest margin since 1984. This will increase inventories of unsold new houses. They’ve already risen from 3.5 months’ supply in October 2020 to 6.0 months in December. Rising costs for everything from lumber to copper will make these houses more expensive and harder to sell. The National Association of Realtors’ index of pending house sales in December fell 7% from a year earlier.