Establishment, firm, or enterprise: does the unit of analysis matter?

Economic data for businesses are usually constructed at the establishment level, the firm level, or the enterprise level. An establishment is a single physical location where one predominant activity occurs. A firm is an establishment or a combination of establishments and, for the purposes of this article, is defined by its unique Employer Identification number (EIN) issued by the Internal Revenue Service (IRS). Firms operate in one industry or in multiple industries. An enterprise is a firm or a combination of firms that engages in economic activities which are classified into multiple industries. An enterprise may report under one or a number of EINs.