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Productivity
Bureau of Labor Statistics > Productivity > Publications > Articles and Research

Higher-frequency Output: Introducing the 12-Month Trailing Average

BLS publishes measures of real sectoral output, sectoral output, and sectoral output price deflator for retail trade industries in its Productivity and Costs by Industry Wholesale Trade and Retail Trade Industries Economic News Release. However, these values are currently only released on an annual basis. To better meet the needs of its customers, the BLS productivity program is exploring new higher-frequency real output measures.[1]

About our measures

Annual output values for retail industries are calculated using sales data from the Census Bureau’s Annual and Monthly Retail Trade Surveys (ARTS and MRTS) for all published years. Industry sales are then broken out by product line using ratios calculated from the Economic Census Product Line Sales, deflated by the corresponding Producer Price Index (PPI) or Consumer Price Index (CPI), and aggregated back to the industry level.

For this experimental measure, BLS continues to use Census, PPI, and CPI as the sources of its sales and deflator data but makes use of their monthly data instead of annual data. Although our annual measures utilize some custom-weighted deflators to better fit certain product line mixes, the experimental measure relies on directly published CPI and PPI data series. The same methods as the published measure are applied to the monthly data to create a monthly output index for each retail industry. These monthly indexes are volatile and reflect significant seasonality, which complicates analysis and comparison to BLS annual values. To reduce the effects of seasonality and provide a measure that is more comparable to our annual measures, BLS introduces an experimental 12-month trailing average output measure for retail trade industries.

The 12-month trailing average takes an average of an industry’s monthly real output value over the previous 12 months. For example, to calculate the 12-month trailing average real output value for January 2018, we take an average of the monthly real output values from February 2017 through January 2018.[3]

This page compares output trends for three retail industries that demonstrate the added analytical and predictive power of the experimental measure: automobile dealers, grocery stores, and clothing stores. The marked December data points along the published annual output line represent the annual values published in our standard release. Each annual data point is connected through linear interpolation and shaded in grey for comparison purposes. The red, dashed line connects the monthly trailing average values. In most industries, the December values for the 12-month trailing average closely align with BLS’s published annual values. While the end-of-year values are largely comparable, the 12-month trailing average provides insight as to when shifts in output occur throughout the year. The productivity program’s most current release of data for retail trade ended in 2022. The 12-month trailing average allows analysts to calculate output values within 20 days of the end of the reference month for all NAICS 3-digit and several NAICS 4-digit retail industries, with values through March 2024 as of this publication, and on a two-month-lag for detailed industries.[4]

Automobile dealers

Chart 1 highlights the relationship between the annual and 12-month trailing average frequencies for automobile dealers (NAICS 4411). From December 2017 through December 2019, the two measures trend closely. While they match up by December of each year, there are clear divergences in the trailing average line following 2019.

Chart data are included in the linked table below.

 

Chart 1 data. Indexes of published and experimental output in automobile dealers (December 2017=100), 2017-24

 

Grocery stores

Chart 2 features an industry with less variation between the two measures for the Grocery Stores Industry. The 12-month trailing average measure reveals a slight period of decline from February through March of 2021, but both frequencies generally trend positively for grocery stores (NAICS 4451).

Chart data are included in the linked table below.

 

Chart 2 data. Indexes of published and experimental output in grocery stores (December 2017=100), 2017-24

 

Clothing stores

Chart 3 showcases clothing stores (NAICS 4481) and reflects the influence of the pandemic on this industry’s output. Both measures declined in 2020, but the trailing average indicates that the real declines in output occurred from March of 2020 through February 2021 which is a level of detail the published annual output cannot capture.

Chart data are included in the linked table below.

 

Chart 3 data. Indexes of published and experimental output in clothing stores (December 2017=100), 2017-24

 

Notes

[1] Due to current data limitations, the inclusion of hours worked and labor productivity are not yet feasible. The BLS productivity program hopes to present experimental versions of these series in the future.

[2] Source: CNSTAT Consensus Panel Study, Recommendation 6: Experimental submodules may address more specialized issues that contribute to the transition in retail trade such as (1) international trade and global value chains; (2) digitization; (3) labor quality; and (4) providing real-time and subsector analyses. Over time, the central module would incorporate improvements developed in the submodules and in new data collection.

[3] Formula depicting the 12-month trailing average:

Formula depiction of the 12-month trailing average for retail output.

 

[4] 14 of the 42 retail trade industries for which BLS publishes 12-month trailing average output values are released on a one-month-lag due to supplemental data from the Census Bureau's Advance Monthly Retail Trade Survey.

Last Modified Date: April 16, 2024