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Consumer Price Index

Quality Adjustment in the CPI: Women’s Bras

Women's bras image

Item definition

The item Women’s Bras is part of the index for Women’s Apparel. It is nested inside the Entry Level Item (ELI) and Item Stratum for Women’s Undergarments, Nightwear, Shapewear, and Swimwear. Here, we examine the hedonic regression model used in the quality adjustment of price data for women’s bras.

CPI sample

The sample used for this hedonic model included 943 observations from an extract of CPI data from August and September 2023 as well as webscraped data from a large national retailer. The CPI data was collected using a larger than usual amount of web-based information due to restrictions on data collection during the COVID-19 pandemic. Basic bras make up about 77 percent of the sample, and national brands comprise 63 percent.

Current Model

Table 1 presents the details of the estimation of the current model used to quality adjust women’s bras.

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


1 3.91796 0.01993 196.59 <.0001

Type: Basic, longline, sports bras


Type: Nursing bras

1 -0.15164 0.07489 -2.02 0.0432 0.92759

Brand: Boutique

1 0.57323 0.04309 13.3 <.0001 0.68912

Brand: High/premium national

1 0.29465 0.02554 11.54 <.0001 0.85792

Brand: National


Brand: Private

1 -0.09167 0.03656 -2.51 0.0123 0.73734

Brand: Miscellaneous

1 -0.53681 0.16823 -3.19 0.0015 0.96682

Closure: Opens partly or completely with front or back fastener


Closure: Pullover with no fastener

1 -0.13874 0.02258 -6.15 <.0001 0.9705

Fiber: Spandex

1 0.00363 0.000963 3.76 0.0002 0.89707

Fiber: Nylon, polyester, rayon


Fiber: Cotton

1 -0.00228 0.00044 -5.2 <.0001 0.93626

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

Summary notes

  • This is the second-ever CPI quality adjustment model for women’s bras, but the first to be used in practice. It was made possible by the use of webscraped data to supplement the CPI sample. This means that fewer women’s bras substitutions will be deemed non-comparable and imputed so long as a model is in use.

    • This is the second hedonic model created for CPI-Apparel that utilizes alternative data.

  • The most important specifications in evaluating substitutions for women’s bras are type, brand type, and fiber content. All of these were included in the model.

  • Multipacks are rare for women’s bras and were not included in the quality adjustment model.

  • Other characteristics like underwire and lining were found to not be statistically significant.


Access data for Women's Apparel 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 23, 2024