Total (new and existing) home inventory is an important measure for gauging and forecasting home prices and home construction impacts. The intuition is clear: more inventory yields weaker or declining home price growth and home building activity. Lean inventory levels lead to price growth and gains for home building.
The metric “months’ supply” is a common measure of current market inventory. For both new and existing home markets.
In the Census May 2024 newly-built home sales data, the current months’ supply of inventory is 9.3. Some analysts have noted that, given the five- to six-month benchmark, that this means the building market for single-family homes is possibly oversupplied, implying declines for construction and prices lie ahead.
According to NAR data, the current months’ supply of single-family homes is just 3.6, well below the five- to six-month threshold. It is this lack of inventory that has produced ongoing price increases despite significantly higher interest rates over the last two years.
Taken together, new and existing single-family home inventory, the current months’ supply of both markets is just 4.4, as estimated for this analysis. This is admittedly higher than the 3.6 reading, using this approach, from a year ago, but it still qualifies as low. See the following graph for total months’ supply going back to the early 1980s using data from the NAR existing home sales series and the Census new home sales data, as calculated by NAHB.
The horizontal axis plots total months’ supply for monthly data going back to the start of 1988 (the starting point of the price data used for this analysis). The vertical axis records the corresponding year-over-year home price growth for the same month as measured by the Case-Shiller Home Price Index. The trend line is estimated using a simple linear regression. The statistical correlation indicates that home price growth, on average, turns negative when inventory reaches an 8-months’ total supply (on the graph, the trend line intersects the horizontal axis, measuring zero percent price growth, at 8 months’ supply).
To be clear, this does not mean that prices will not fall until months’ supply exceeds eight. For example, 24% of the data registering 6.5 to 7.5 months’ supply recorded home price declines. For the data in the range of 7.5 months’ supply to less than 8 months’ supply, this share increased to 36%. Overall, for months with less than an eight months’ supply, it was less likely than not to see home price declines, but it did happen in certain market conditions.
With each Census new home sales report, NAHB will continue to estimate and watch the total months’ supply measure. But given this analysis, at 4.4 total months’ supply, inventory levels have increased but remain low and supportive of limited gains for home building and upward pressure on nominal home prices.
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