Fortune changed its methodology in 1994 to include service companies in the Fortune 500. Before that change, the principal ranking was limited largely to manufacturing, mining and energy-exploration businesses.
Fortune had long published separate rankings for major service industries, including commercial banks, utilities, life insurers, retailers and transportation companies. Combining these sectors made the main list better reflect the changing U.S. economy, in which finance, retail, communications, health care and other services were becoming increasingly important.
The revision had a dramatic effect: 291 service companies entered the famous ranking, including three companies that landed in its top 10. The change also made year-to-year comparisons more complicated, because some companies were appearing on the main list for the first time due to eligibility rules rather than sudden growth.
The first combined ranking was published in 1995 using 1994 revenue data, which explains why some accounts describe the transformation as a 1995 change. For the methodology question itself, however, Fortune’s stated year is 1994. The reform also helped establish the modern Fortune 500 as a revenue ranking spanning both industrial and service businesses.