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

Quality Adjustment in the CPI: Women’s Boots, Shoes, Sandals, and Slippers

Women's footwear image

Item definition

The Entry Level Item (ELI) category of Women’s Footwear is part of the index for Footwear. It includes two categories: (1) women’s casual or dress shoes, boots, sandals, and house slippers, and (2) women’s athletic footwear. Here, we examine the hedonic regression model used in the quality adjustment of price data for the first group, women’s boots, shoes, sandals, and slippers.

CPI sample

The sample used for the current hedonic model for women’s boots, shoes, sandals, and slippers included 1,523 observations from an extract of CPI data for the months of March and April 2022. The model was constructed using web-based information due to restrictions on data collection during the COVID-19 pandemic, unlike models from the past that had a mix of store and website data. There were more than 400 unique brands in the sample, with most brands having fewer than 20 observations. Additionally, the sample included more than 100 outlets of both the brick and e-commerce variety; the top outlet was about 10 percent of the sample.

Current Model

Table 1. Parameter estimates for the hedonic regression for women's footwear
Variable DF Parameter Estimate Standard Error T Statistic Pr > |t| Tolerance Statistic

Intercept

 1 4.49857 0.03454 130.23 <.0001

Type: Above knee boot

 1 0.49266 0.1315 3.75 0.0002 0.89462

Type: Mid-calf to knee boot

 1 0.21094 0.06284 3.36 0.0008 0.79318

Type: Below mid-calf boot

 1 0.11488 0.03591 3.2 0.0014 0.56555

Type: Sandal

 1 -0.14433 0.02922 -4.94 <.0001 0.59418

Type: Slipper

 1 -0.40441 0.04179 -9.68 <.0001 0.77094

Type: Shoe

 Base

Upper Material: Man-made

 1 -0.41967 0.02754 -15.24 <.0001 0.62063

Upper Material: Fabric

 1 -0.343 0.03328 -10.31 <.0001 0.69251

Upper Material: Combination

 1 -0.13663 0.04862 -2.81 0.005 0.90041

Upper Material: Leather

 Base

Outsole: Leather

 1 0.11036 0.05585 1.98 0.0483 0.8704

Outsole: Man-made

 Base

Brand: Exclusive

 1 1.35344 0.07217 18.75 <.0001 0.7427

Brand: Premium national

 1 0.34165 0.03594 9.51 <.0001 0.71857

Brand: Private

 1 -0.26807 0.03495 -7.67 <.0001 0.90558

Brand: Miscellaneous

 1 -0.2945 0.06758 -4.36 <.0001 0.7831

Brand: National

 Base

Heel Height: >3 inches

 1 0.31453 0.04055 7.76 <.0001 0.78795

Heel Height: 2-3 inches

 1 0.19202 0.03567 5.38 <.0001 0.75775

Heel Height: 1-2 inches

 1 0.14303 0.02678 5.34 <.0001 0.68598

Heel Height: <1 inch

 Base  

Closure: Buckle

 1 0.11026 0.03547 3.11 0.0019 0.72429

Closure: Zipper

 1 0.18765 0.04177 4.49 <.0001 0.60707

Closure: Velcro

 1 0.1803 0.0539 3.35 0.0008 0.87066

Closure: Laces

 1 0.16489 0.03928 4.2 <.0001 0.80507

Closure: No closure

 Base

Note: This model contains control variables for type of business, type of store, and geographic region, but they are not used in adjustments.

Summary notes

  • Quality adjustments derived from hedonic regressions for women’s boots, shoes, sandals, and slippers were first incorporated into the CPI in 1995. Since then, the model for women’s boots, shoes, sandals, and slippers has been updated five times.
  • For women’s boots, shoes, sandals, and slippers, the characteristics that receive the most focus during model evaluation include footwear type, upper material, outsole material, and brand category, though other specifications can be important as well. Some footwear hedonic models have adjustments for specific brands, but this data did not demonstrate a need for that given the diversity of the sample.
  • Two variables in the model are applied differently than in previous models.
    • First, the closure variable was re-included for the first time since 2011. The prior model was unable to find a statistically significant relationship between closure and price given the other variables and the data. This time, however, all closure types—buckles, zippers, Velcro, and laces—were significant and can be used for quality adjustments. As expected, the various closures add value as compared to no closure.
    • Secondly, the heel variable was changed to allow for more gradation between sizes. As expected again, higher heel heights are associated with higher prices.
  • This model was constructed using web-based information due to restrictions on data collection during the COVID-19 pandemic, unlike models from the past that had a mix of store and website data.

Data

Access data for Footwear 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: February 22, 2023