One of the preeminent virtues of the Economic Census program is that comparable data have been collected at fixed intervals and with consistent definitions across decades. Nonetheless, census reports typically included very little historical data. Comparative statistics, covering the current and most recent previous census, include data only for the United States and states. Left to the user is the assembly of time series--such as the growth of retailing in a particular area, or trends in a particular manufacturing industry.
Acquiring Reports from Previous Censuses
All 2002, 1997, and 1992 census publications are available on the web in portable document format (pdf). Collections of historical census reports, are maintained at certain major libraries, and individual reports may be borrowed through interlibrary loan. The Census Customer Services will photocopy historical printed reports for a fee.
Many of these data are also available in machine-readable form. CD-ROM or DVD-ROM coverage of the 2002 and 1997 Economic Census is complete, and CD-ROMs for 1992 and 1987 exclude only "Miscellaneous Subjects" reports. Further, the 1992 and 1987 CD-ROMs also include selected data covering earlier time periods. Volume 1j of the 1992 CD-ROM series includes a national time series from the Annual Survey of Manufactures from 1958 to 1995, and monthly retail sales from 1967 to 1994. Volume 4 of the1992 CD-ROM series, entitled "Nonemployer Statistics", includes limited Geographic Area Series files for 1987 for retail trade, wholesale trade, service industries, and manufacturing, as well as 1982 data for manufacturing, in formats that mirror their 1992 counterparts. More comprehensive data for 1987, and a few data sets for 1982 and 1977 are included on the final 1987 Economic Census CD-ROMs (1e and 2).
Key files from the 1972, 1977, and 1982 economic censuses were issued on computer tape. Many of these files may be obtained from the National Archives and Records Administration.
County Business Patterns, available at this site for years back to 1994, is available on CD-ROM back to 1986. The University of Virginia Library maintains a lookup tool for CBP data at the 2-digit SIC level for 1977 to 1997.
Industry Comparability: NAICS and SIC
The implementation of NAICS in 1997 caused major disruptions in the availability of comparable information across time periods. In recent history, the SIC system was updated 3 times (in 1967, 1972, and 1987) and each time a significant number of new industries was introduced into the existing framework. What was different for 1997 was that the whole framework was changed.(1)
While data for nearly half of the SIC's in use in 1992 can derived from 1997 NAICS industries, a substantial number of SIC industries cannot be much more than approximated under NAICS. That makes the 1997 Economic Census particularly important, because census questionnaires identified industry components finely enough that data could be categorized under either NAICS or SIC; and as a result certain key data were published according to the old system as well as the new. The Comparative Statistics, 1997 and 1992 report presents the number of establishments, sales, employment and payroll for each SIC for the nation and each state, for both 1997 and 1992. Thus, basic SIC-by-state time series can be carried backward from 1997 to 1987, and farther to the extent that particular industries are not affected by SIC changes in 1987, 1972, and 1967.
NAICS time series can go forward from 1997, but they cannot generally go backward to earlier years, because many NAICS categories require information that was not collected in 1992 and earlier censuses. For instance, NAICS 45321, Office Supplies and Stationery Stores, differs from SIC 5943, Stationery Stores, primarily by the addition of certain office supply stores that were previously classified in wholesale trade. Census questionnaires prior to 1997 did not separately differentiate office supply stores from other kinds of office supply wholesalers, so NAICS 45321 cannot be estimated for prior periods.(2)
The Census Bureau has estimated some national-level NAICS time series back to 1992. That project, intended to support time series for monthly surveys, is limited to broad industry categories within manufacturing, retail trade and wholesale trade.
Users have access to correspondence tables between the old and new systems at the NAICS website and in the formal NAICS 97 Manual. These tables show for each NAICS industry the SIC categories or parts thereof that comprise them, and for each SIC industry the NAICS industries or parts thereof to which their establishments are likely to be reclassified. The 1997 Economic Census Bridge between NAICS and SIC report takes that correspondence a significant step farther by showing the number of establishments, sales, employment, and payroll at the national level for each of those intersections between the old and new systems. For example, the Bridge report shows that the office supply stores that were transferred into retail trade from wholesale trade increased sales of the new retail Office Supply and Stationery Stores category by nearly ten-fold over the SIC industry of the same name.
The Bridge tables are so powerful that one might be tempted to "update" historical figures by SIC to NAICS by applying proportions derivable from the tables. The user should employ such "synthetic estimation" with caution, however, since nationwide proportions may not reflect relationships in particular geographic areas or in prior time periods. Many new industries reflected in NAICS did not exist to a significant extent in prior periods, for example, satellite telecommunications.
At broader levels of classification, the changes between SIC and NAICS were further confounded by the rearrangement of the hierarchy. For example, the service industries division of the SIC was subdivided into five new NAICS sectors and parts of four others. Less noticeable, but perhaps more troublesome, are shifts affecting sectors--like manufacturing, wholesale trade, and retail trade--that retained their status as sector titles in NAICS but were being affected by changes in scope. Retail trade became smaller under NAICS than under SIC just because eating and drinking places, which accounted for roughly 10 percent of SIC-based retail sales and a third of SIC-based retail employment, were transferred to the new Accommodation and Food Services sector. Retail losses were offset partially by transfers between retail and wholesale trade, such as the office supply stores mentioned above. Manufacturing also shrank somewhat under NAICS because significant components were reclassified elsewhere.
Industry Changes, 2002 and 2007
Further changes were made to NAICS for 2002, but these modifications did not affect the comparability of sector totals. Industries were redefined within construction and wholesale trade, and there was some rearrangement of industries within the information sector. Several new industries were defined within information and retail trade without disrupting the availability of data comparable to that published for 1997. The Bridge Between 2002 NAICS and 1997 NAICS details differences of two types: (a) changes between NAICS 2002 and NAICS 1997 and (b) features of NAICS 1997 introduced too late for implementation in the 1997 Economic Census. Comparative Statistics as issued from the 2002 Economic Census reclassifies 2002 data according to the 1997 NAICS and presents 2002 and 1997 data side by side on a comparable basis for the nation and states.
Changes between 2002 NAICS and 2007 NAICS were relatively minor, but do affect four sector totals. Since nearly all industries are comparable 2002 to 2007, year to year comparisons are easy to make.
NAICS 2007 introduces two new industries: biotech research and development and executive search services. At the same time several industries in the information sector have been consolidated: paging into wireless telecommunication; cable program distribution and most ISPs into wired telecommunication; web search portals into Internet publishing and broadcasting. Real estate investment trusts (REITs) are dispersed and mostly moved from from the Finance and Insurance sector to Real Estate.
Selected 2007 Economic Census data will be published according to the 2002 NAICS to allow precise comparisons between 2002 and 2007 data: preliminary national totals in the Advance Report, a detailed Bridge showing the relationships between 2007 and 2002 NAICS categories that changed, and state level Comparative Statistics after the publication of geographic area data by 2007 NAICS.
Scope of Economic Census Programs
Prior to 1992, the Economic Census program covered less of the American economy. In 1987 and earlier years, the census did not include Finance, Insurance and Real Estate; and it included only selected transportation industries within the Transportation, Communication, and Utilities sector. The addition of those components boosted census coverage from roughly 76 percent of the gross domestic product in 1987 to about 98 percent in 1992 (counting the separtely conducted economic census and censuses of governments and agriculture). The coverage of service industries expanded in 1967, 1977, and 1987. Thus, time series available for some industries are shorter than others.
Geographic Comparability
Most students of economic trends confine themselves to looking at the nation, states, and counties. County boundary changes are few and far between, while many places, metropolitan areas, and ZIP Codes change boundaries over time. Metropolitan areas are redefined after each population census and new criteria are generally introduced at that point. Most metropolitan areas tabulated for 2007 are defined the same as they were for 2002, while most metro areas were redefined between the 1997 and 2002 censuses. There are maps that illustrate the 1997 to 2002 metro area changes.
1. Paul T. Zeisset & Mark E. Wallace, "How NAICS Will Affect Data Users", published on the Internet at http://www.census.gov/epcd/www/naicsusr.html.
2. Ibid.
