U.S. Department of Commerce

Monthly & Annual Retail Trade

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Advance Monthly Retail Trade Survey Methodology

Overview

The U.S. Census Bureau conducts the Advance Monthly Sales for Retail and Food Services Survey (MARTS) to produce early national estimates of total and month-to-month change in sales for retail and food service establishments located in the United States. A retail establishment is one that sells merchandise to the general public (final consumers). The estimates from MARTS are released approximately nine business days after the end of the reference month and are revised one month later by estimates from the Monthly Retail Trade and Food Services Survey (MRTS). Estimates are summarized by industry classification based on the North American Industry Classification System (NAICS).

Sampling Frame

Companies or Employer Identification Numbers (EINs) selected in the Monthly Retail Trade Survey (MRTS).

Sample Design

The MARTS is a sample of approximately 4,900 units (companies and EINs) selected from the MRTS sample of about 12,000 units. The MARTS units are stratified by somewhat broader industry categories and substratified by monthly sales as measured in the Monthly Retail Trade Survey. There are 36 primary strata defined by industry and three to twelve size substrata for each primary stratum. Sample sizes are calculated to meet hypothetical reliability constraints on estimated monthly sales totals for specified industries. Sample selection is done independently within each size stratum using a systematic probability-proportional-to-size procedure where the size used is the MRTS sampling weight. Sampling weights range from 1 to 1,000. No births are added to the MARTS sample. Instead, we redesign and reselect the sample for MARTS approximately every 2½ to 3 years.

Data Collection

Data are collected by mail, facsimile, or telephone from approximately 4,900 employer firms. Collection units may be companies, parts of companies (defined by Employer Identification Numbers (EINs) or divisions of diversified companies), or single unit establishments (also defined by EINs). We request data for activity taking place during the calendar month. Followup is conducted by telephone beginning on the third business day after the reference month. Data collection is completed by the sixth business day following the end of the reference month. Response to the survey is voluntary. Nonresponding firms are accounted for via the estimation method. Data from nearly 1.8 million firms without paid employees, or nonemployers, are represented in the published estimates through the estimation procedure.

Estimation and sampling variance

Advance sales estimates for the most detailed industries are computed using a type of ratio estimator known as the link-relative estimator. For each detailed industry, we compute a ratio of current-to-previous month weighted sales using data from units for which we have obtained usable responses for both the current and previous month. The For each detailed industry, the advance total sales estimates for the current month is computed by multiplying this ratio by the preliminary sales estimate for the previous month (derived from the larger MRTS) at the appropriate industry level. Total estimates for broader industries are computed as the sum of the detailed industry estimates. Note that the preliminary sales estimate used in this computation includes data for nonemployers; therefore, nonemployers are represented in the published MARTS estimates. The link relative estimate is used because we do no sampling-unit level imputation or adjustment for nonrespondents in MARTS. This estimator differs from the usual ratio estimator because it does not estimate monthly totals prior to estimating the month-to-month change. Variances are estimated using the method of random groups and are used to determine if measured changes are statistically significant.

Benchmarking

Estimates are benchmarked to annual survey estimates via the estimation method.

Seasonal Adjustment

Estimates are adjusted for seasonal variation and holiday and trading-day differences using the Census Bureau's X-13ARIMA-SEATS program using the X-11 filter-based adjustment procedure.

Important uses of results

Retail sales are one of the primary measures of consumer demand for both durable and non-durable goods. They are used as inputs for estimating personal consumption expenditures.


Source: U.S. Census Bureau | Monthly & Annual Retail Trade | (301) 763-2713 |  Last Revised: May 31, 2013