Census of Service Industries, published every five years. The most recent edition, for 1987, divides revenues in the industry between firms subject to federal income tax (91 percent of the total) and tax-exempt, or not-for-profit, institutions (9 percent).17
These data do not, however, capture the full scale of third-party testing. Many of the more than 400 members of the American Council of Independent Laboratories (ACIL), the industry association for testing laboratories, are classified as engineering services firms rather than laboratories.18 These firms are members of ACIL because a significant share of their business consists of testing services. Their revenues from testing are not, however, separately identified in the Census Bureau data.19 Engineering services totaled $61.5 billion in revenue in 1992.20 When the number and size of ACIL members that identify themselves as engineering services firms are taken into account, and the Census data are scaled accordingly, independent laboratory services in the United States are estimated to be a $10.5 billion industry.
Testing services encompass a broad spectrum of technical activities and competencies. The International Organization for Standardization (ISO) definition of a test, in the context of conformity assessment, is a "technical operation that consists of the determination of one or more characteristics of a given product, process or service according to a specified procedure."21 Materials, parts, and completed products may all be tested for their physical properties, such as strength and durability; physical dimensions; electrical characteristics, including interference with other electrical devices; acoustical properties; chemical composition; presence of toxic contaminants; and multitudes of other features.
Testing laboratories serve several categories of clients. The 1987 Census of Service Industries separates the receipts of independent testing laboratories, by class of client, into 8.7 percent federal government, 4.9 percent state and local governments, and 86.4 percent other clients—mainly private industry. Manufacturers rely on independent testing as a check against their own tests. Testing against specific standards provides independent data to support manufacturer's declarations of conformity to purchaser specifications or government regulations. Purchasers—including large manufacturers and government procurement agencies—rely on third-party testing to verify the conformity of parts and products to their stated specifications. Regulations frequently require manufacturers to show compliance through results of independent testing. The Occupational Safety and Health Administration (OSHA), for example, requires equipment used in the workplace to be tested by an independent laboratory accredited under OSHA's Nationally Recognized Testing Laboratory (NRTL) program.22
Certification is a form of conformity assessment that involves determining whether a product, process, or service meets a specific standard or set of standards.