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Consumer Price Index
Bureau of Labor Statistics > Consumer Price Index > Methods > Quality Adjustment

Quality Adjustment in the CPI: Ranges and Cooktops

Ranges and cooktops decorative image

Item definition

The entry level item (ELI) category of ranges and cooktops is part of the index for major appliances. In this factsheet, we examine the regression model used in the quality adjustment of price data for ranges.

CPI sample

The sample used for the new hedonic model included approximately 1,600 observations.  The model was constructed from a dataset of prices and product specifications as of December 2024 from a third-party source. Built-in wall ovens were excluded from the sample used for modeling.  

Current Model

There are two separate models – one for gas ranges and one for electric ranges.

Table 1 presents the details of the current model used to quality adjust electric ranges.

Table 1. Parameter estimates for the hedonic regression for electric ranges
Variable Name DF Parameter Estimate Standard error t Value Pr > |t| Tolerance

Intercept

 1 5.33591 0.14234 37.49 <.0001

Drawer Type: Storage drawer

 1 -0.3455 0.03467 -9.96 <.0001 0.45173

Induction Heating

 1 0.42254 0.03376 12.52 <.0001 0.51032

Controls on Front of Range

 1 0.44786 0.03032 14.77 <.0001 0.66641

Product Width (Continuous Variable)

 1 0.02577 0.00447 5.76 <.0001 0.66229

Product Weight (Continuous Variable)

 1 0.00244 0.0001809 13.47 <.0001 0.38584

Self-Cleaning Oven

 1 0.44402 0.03732 11.9 <.0001 0.83319

Length of Warranty (Continuous Variable)

 1 0.35047 0.04121 8.5 <.0001 0.36586

Table 2 presents the details of the current model used to quality adjust gas ranges.

Table 2. Parameter estimates for the hedonic regression for gas ranges
Variable Name DF Parameter Estimate Standard error t Value Pr > |t| Tolerance

Intercept

 1 7.06945 0.19938 35.46 <.0001

Luxury Brand # 1

 1 0.3449 0.04975 6.93 <.0001 0.59376

Drawer Type: None

 1 0.2388 0.03263 7.32 <.0001 0.48649

Product Width (Continuous Variable)

 1 0.01345 0.00266 5.05 <.0001 0.34227

Summary notes

  • Quality adjustments derived from hedonic regressions for Ranges were first used in the CPI in 2008. The previous hedonic model included the following variables: oven style, power source, number of burners/elements, bridge elements, color, expandable elements, convection ovens, and manual cleaning. The variables in the new model reflect changes in the market and in customer preferences.

  • Induction: some electric stoves produce heat when in contact with a magnetic field, such as an iron or steel pan.

  • Length of Warranty: Most appliances come with a manufacturer's warranty. Some warranties distinguish between parts and labor, but this model captures the length of warranty only. Length of Warranty is a continuous variable and positively influences the price for both gas and electric ranges.

  • The Self-cleaning oven variable accounts for an oven that automatically cleans itself when the cleaning function is initialized. The self-cleaning cycle uses high heat to burn off spills and splatters within the oven and adds value to the product.

  • Storage drawer is an accessory drawer, usually below the oven, used for storing pans and cooking sheets. However, it takes away cooking space, and thus, the storage drawer variable negatively influences the price.

  • The log of regular price is the dependent variable.

  • The R2 statistics were 0.922 for the Gas model and 0.942 for the Electric model. These values indicate that approximately 92 and 94 percent of the variation in price are explained by each hedonic regression model, respectively.

Data

Access data for major appliances in our online database.

Additional information

Additional information may be obtained from the Consumer Price Index Information Office by email or calling 202-691-7000. Information on the CPI's overall methodology can be found in the BLS Handbook of Methods.

Last Modified Date: June 30, 2025