In the 1970s, the employment practices of most U.S. corporations began to change. The first indication of change was the rapid growth in temporary employment. Prior to the 1970s, temporary employment agencies were generally limited to providing short-term secretarial help, day laborers, and nursing services. However, around 1975, temporary employment agencies began to provide workers for many other types of jobs, including maintenance work, custodial services, legal services, and computer programming. Corporations began to utilize outside contractors to provide workers for jobs that had previously been done in-house, including such core firm tasks as inventory control, bookkeeping, and even human resources. Between 1980 and 1989, the number of employees working for temporary agencies doubled from 518,000 to 1,032,000. In 1993, Fortune magazine reported that Manpower, Inc. had become the largest employer in America. The number of employees hired by temporary agencies continued to rise throughout the 1990s, so that by 2001, nearly two million workers worked for temporary employment agencies, many of whom were in highly skilled positions. As of May 2001, according to the U.S. Department of Labor, 9.1 percent of all temporary workers were executives and managers, while only 13 percent were low-skilled laborers. A survey of private firms in all industries and of all sizes conducted by the Upjohn Institute in 1996 found that some 78 percent of private sector firms used flexible staffing arrangements – a significant increase from a decade earlier.

In the late 1970s, corporations began to make other changes in their human resource practices.