The NAHB/Wells Fargo Housing Market Index (HMI) is based on a monthly survey of NAHB members designed to take the pulse of the single-family housing market. The survey asks respondents to rate market conditions for the sale of new homes at the present time and in the next six months as well as the traffic of prospective buyers of new homes.
The HMI is a weighted average of separate diffusion indices for these three key single-family series. The first two series are rated on a scale of Good, Fair and Poor and the last is rated on a scale of High/Very High, Average, and Low/Very Low. A diffusion index is calculated for each series by applying the formula “(Good-Poor+100)/2” to the present and future sales series and “(High/Very High – Low/Very Low + 100)/2” to the traffic series. Each resulting index is then seasonally adjusted and weighted to produce the HMI.
Based on this calculation, the HMI can range between 0 and 100.