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Monthly & Annual Wholesale Trade

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How Surveys are Collected

Annual Methodology

Confidentiality: Title 13 of the United States Code authorizes the Census Bureau to conduct censuses and surveys. Section 9 of the same Title requires that any information collected from the public under the authority of Title 13 be maintained as confidential. Section 214 of Title 13 and Sections 3559 and 3571 of Title 18 of the United States Code provide for the imposition of penalties of up to five years in prison and up to $250,000 in fines for wrongful disclosure of confidential census information. The Census Bureau's internal Disclosure Review Board sets the confidentiality rules for all data releases. A checklist approach is used to ensure that all potential risks to the confidentiality of the data are considered and addressed.

Disclosure Statement: A disclosure of data occurs when an individual can use published statistical information to identify either an individual or firm that has provided information under a pledge of confidentiality. Disclosure limitation is the process used to protect the confidentiality of the survey data provided by an individual or firm. Using disclosure limitation procedures, the Census Bureau modifies or removes the characteristics that put confidential information at risk for disclosure. Although it may appear that a table shows information about a specific individual or business, the Census Bureau has taken steps to disguise or suppress the original data while making sure the results are still useful. The techniques used by the Census Bureau to protect confidentiality in tabulations vary, depending on the type of data.

Sampling Frame: Companies, parts of companies (defined by Employer Identification Numbers, or EINs), and single-unit establishments (also defined by EINs) that are located in the United States, have paid employees, and are classified in wholesale trade as defined by the 2007 NAICS. This includes wholesalers that take title to the goods they sell such as jobbers, industrial distributors, exporters, importers, and Manufacturers’ Sales Branches and Offices (MSBOs), as well as companies that do not take title of the goods they sell such as agents, merchandise or commodity brokers, commission merchants, and electronic business-to-business markets. The EIN is the identifier employer businesses use to report Social Security payroll withholdings to the Federal government. Read more [PDF] about the AWTS sampling frame.

Sample Design and Size: The sample for AWTS consists of three separate samples: (1) a sample of merchant wholesalers, excluding MSBOs, (2) a sample of MSBOs, and (3) a sample of wholesale electronic markets and agents and brokers. AWTS uses a stratified, one-stage design with primary strata defined by industry (e.g., Motor Vehicle and Motor Vehicle Parts, Furniture and Home Furnishings, Grocery, etc.). There are 59 primary strata: 42 from the merchant wholesale sample, 17 from the MSBOs sample, and 2 from the Agents and Brokers sample. The primary strata are substratified into 4, 7, 10, or 13 annual sales size strata. The largest sales size stratum within each industry stratum consists of companies, all of which are selected with certainty (sampling weight equal to one). The other strata are populated by EINs. Sample sizes are computed to meet multiple coefficient of variation constraints on estimated annual sales and end-of-year inventory totals. Constraints are specified at detailed industry levels and at broad levels up to the total wholesale level. Sampling weights range from 1 to 250. Units are selected independently between strata using simple random sampling without replacement within the size substrata. The sample consists of approximately 2,100 certainty companies and 5,900 EINs. Updates to the sample are made on a quarterly basis to account for new businesses, deaths, and other changes to the universe. Read more [PDF] about how the AWTS sample is maintained.

Data Collection: Data are collected by mail, fax, Internet, and telephone. Response is mandatory under the authority of an Act of Congress, Title 13, United States Code, Sections 182, 224, and 225. Firms in the AWTS sample are asked to report their data for the year just ending. Two years of data are requested in the year in which a new sample is introduced.

Data Items Requested: Data items requested include annual sales, e-commerce sales, number of establishments covered by the report, value of inventories, inventory by valuation, inventory outside of the United States, total purchases of products, total operating expenses and the ending date of the report period if the data provided are for a period other than the calendar year. Sales tax and detailed operating expense items are requested every 5 years, with the most recent collection in 2012.

Estimation and Sampling Variance: Total estimates are computed using the Horvitz-Thompson estimator (i.e., as the sum of weighted data (reported or imputed) for all selected sampling units that meet the sample canvass and tabulation criteria). The weight for a given sampling unit is the reciprocal of its probability of selection into the AWTS sample. These estimates are input to a benchmarking procedure, as described below. Variances are estimated using the method of random groups and are used to determine if measured changes are statistically significant. Read more [PDF] about how the AWTS arrives at its estimates and the reliabilty of those estimates. Additional information regarding the quality of AWTS data is available upon request.

Response Rates: Economic surveys at the Census Bureau are required to compute two different types of response rates: a unit response rate and weighted item response rates. Read more [PDF] about AWTS response rates (including the 2013 rates).

Linking Samples

Sales estimates from the new sample for reference year 2010 and subsequent years are linked to the prior sample estimates by multiplying the Horvitz-Thompson estimates from the new sample by a ratio. The ratio is calculated as follows:

  • The numerator is the 2010 published, census-adjusted (based on the 2007 Economic Census) sales estimate for the industry on a 2007 NAICS basis from the prior sample.
  • The denominator is the 2010 Horvitz-Thompson sales estimate for the industry on a 2007 NAICS basis from the new sample.

The resulting sales estimates (call these “modified” sales estimates) are implicitly benchmarked to 2007 Economic Census results via this linking procedure. The following method is used to produce “modified” estimates for the following items: end-of-year inventories, total operating expenses, purchases, and e-commerce. First, the sales ratio described above is multiplied by the Horvitz-Thompson estimate for the given item for 2010 and subsequent years. Then the published estimates for 2004 through 2010 from the prior sample are input into the benchmarking program. Using this program, the estimates for 2005 through 2010 for each detailed industry are revised in a manner that:

  • Uses the benchmarked estimate for 2004 from the prior sample as a constraint, resulting in no revision to the 2004 estimate.
  • Uses the ‘modified’ estimate for 2010 from the new sample as a constraint.
  • Minimizes the sum of squared differences between the year-to-year changes of the input and revised estimates for 2005 through 2010.

A similar method is used for foreign inventories, only using the benchmarked estimate for 2005 from the prior sample as a constraint, because foreign inventories was not collected for 2004.

For Wholesale Electronic Markets and Agents and Brokers (NAICS 425), sales estimates (i.e., gross selling value plus sales on own account) from the new sample for 2010 and subsequent years are linked to the prior sample estimates by multiplying the Horvitz-Thompson estimates from the new sample by a ratio. The ratio is calculated as follows:

  • The numerator is the 2010 published, census-adjusted estimate of gross selling value plus sales on own account for the industry on a 2007 NAICS basis from the prior sample.
  • The denominator is the 2010 Horvitz-Thompson estimate of gross selling value plus sales on own account for the industry on a 2007 NAICS basis from the new sample.

The following method is used to provide “modified” estimates for the following items: commissions, gross selling value, operating expenses and sales on own account. First the sales ratio described above is multiplied by the Horvitz-Thompson estimates for the given item for 2010 and subsequent years. Then the published estimates for 2004 through 2010 from the prior sample are input into the benchmarking program. Using this program, the estimates for 2005 through 2010 for each detailed industry are revised in a manner that:

  • Uses the benchmarked estimate for 2004 from the prior sample as a constraint, resulting in no revision to the 2004 estimate.
  • Uses the ‘modified’ estimate for 2010 from the new sample as a constraint.
  • Minimizes the sum of squared differences between the year-to-year changes of the input and revised estimates for 2005 through 2010.

To ensure additivity, estimates of gross selling value and sales on own account are raked to the modified sales estimate.

Modified estimates at aggregate industry levels are computed by summing the modified estimates for the appropriate detailed industries comprising the aggregates.

Benchmarking

Preliminary results of the 2012 Economic Census are now available and used to benchmark AWTS estimates. Revisions to 2007 Economic Census results are also available reflecting changes to sales in NAICS 4247. The modified sales estimates are input to the benchmarking program. Using this program, they are revised in a manner that:

  • Uses the 2012 Economic Census sales total as a constraint, along with the existing 2007 modified sales estimate, which is already linked to the 2007 Economic Census.
  • Minimizes the sum of squared differences between the year-to-year changes of the input and revised estimates for 2008 through 2013.
  • In the case of NAICS 4247, there are three constraints: the 2012 Economic Census sales total, the revised 2007 Economic Census sales total, and the 2002 modified sales estimate, which is already linked to the 2002 Economic Census. The same sum of squared differences is then minimized for 2003 through 2013.

The process is applied separately to merchant wholesalers except MSBOs and to MSBOs. The same process is applied to Wholesale Electronic Markets and Agents and Brokers (NAICS 425) using sales estimates defined as gross selling value plus sales on own account. Refer to the estimates output from this operation as “benchmarked.”

A similar method to the one for adjusting sales is used to adjust estimates for inventories, purchases, operating expenses, e-commerce, and EDI. Each of these items except operating expenses and foreign inventory are revised in the following manner:

  • 2002, 2007, and 2012 modified estimates are multiplied by the ratio of benchmarked sales divided by modified sales for the same year.
  • Modified estimates for each item are input into the benchmarking program using the three constraints calculated above.
  • The benchmarking program minimizes the sum of squared differences between the year-to-year changes of the input and revised estimates for 2003 through 2013.
  • Note that unless the 2007 Economic Census sales value was revised, the benchmarked estimates will equal the modified estimates for the years 2007 and earlier.

Operating expenses and foreign inventories do not have 2002 estimates available, so only two constraints are input to the benchmarking program: the 2007 and 2012 modified item estimates multiplied by the ratio of benchmarked sales to modified sales for the same year. This method allows adjustments all the way back to the beginning of the series.

For Wholesale Electronic Markets and Agents and Brokers, a similar process is applied to adjust estimates for commissions and operating expenses. They are revised in the following manner.

  • 2007 and 2012 modified estimates are multiplied by the ratio of benchmarked gross selling value plus sales on own account divided by modified gross selling value plus sales on own account for the same year.
  • Modified estimates for each item are input into the benchmarking program using the two constraints calculated above.
  • The benchmarking program minimizes the sum of squared differences between the year-to-year changes of the input and revised estimates from the beginning of the series through 2013.

Benchmarked estimates at aggregate industry levels are computed by summing the benchmarked estimates for the appropriate detailed industries comprising the aggregate, and benchmarked estimates for merchant wholesales are computed by summing the benchmarked estimates for MSBOs and merchant wholesalers except MSBOs.


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Source: U.S. Census Bureau | Service Sector Statistics Division | Last Revised: April 03, 2015