1. U.S. Department of Labor, “Employee Tenure in 2002” (Washington, D.C.: Government Printing Office, 2002); and U.S. Department of Labor, “Number of Jobs Held, Labor Market Activity, and Earnings Growth Among Younger Baby Boomers — Results From More Than Two Decades of a Longitudinal Survey” (Washington, D.C.: Government Printing Office, 2004).
2. These numbers are for external hires. Internal transfers get up to speed about twice as fast. See R. Williams, “Mellon Learning Curve Research Study” (New York: Mellon Corp., 2003).
3. This study was based on the U.S. Department of Labor’s National Longitudinal Survey and uses a representative sample of mostly early-career workers in the United States. See D.N. Dickter, M. Roznowski and D.A. Harrison, “Temporal Tempering: An Event History Analysis of the Process of Voluntary Turnover,” Journal of Applied Psychology 81 (1996): 705–716.
4. See, for example, R. Moreland, “Social Categorization and the Assimilation of ‘New’ Group Members,” Journal of Personality and Social Psychology 48 (1985): 1173–1190; D.J. Nash and A.W. Wolfe, “The Stranger in Laboratory Culture,” American Journal of Sociology 78 (1957): 399–417; and R.C. Ziller, R.D. Behringer and M.J. Jansen, “The Newcomer in Open and Closed Groups,” Journal of Applied Psychology 45 (1961): 55–58.
5. Turnover costs include lost productivity resulting from a vacancy, search fees, management time for interviews and training the replacement. Ten percent of companies report the average cost as more than $40,000. See R. McNatt and L. Light, “Job Turnover Tab,” Business Week, April 20, 1998, 8.
6. The entire AT&T study is described in D.W. Bray and A. Howard, “The AT&T Longitudinal Studies of Managers” in “Longitudinal Studies of Adult Psychological Development,” ed. K.W. Schaie (New York: Guilford Press, 1983). Further support for the importance of a challenging assignment is found in D.E. Berlew and D.T. Hall, “The Socialization of Managers: The Effects of Expectation on Performance,” Administrative Science Quarterly 11, no. 2 (1966): 207–223; and H.G. Kaufman, “Relationship of Early Challenge to Job Performance, Professional Contribution, and Competence of Engineers,” Journal of Applied Psychology 59 (1974): 377–379.
7. See, for example, S.C. de Janasz, S.E. Sullivan and V. Whiting, “Mentor Networks and Career Success: Lessons for Turbulent Times,” Academy of Management Executive 17 (November 2003): 78–92; E.A. Fagenson, “The Mentor Advantage: Perceived Career/Job Experiences of Proteges vs. Non-Proteges,” Journal of Organizational Behavior 10 (1989): 309–320; and G.T. Chao, P.M. Walz and P.D. Gardner, “Formal and Informal Mentorships: A Comparison on Mentoring Functions and Contrast With Non-Mentored Counterparts,” Personnel Psychology 45 (1992): 619–636.