Peter Drucker, in his widely esteemed book The Essential Drucker, wrote in 2001 that “Executives spend more time on managing people and making decisions than on anything else, and they should.  No other decisions are so long lasting in their consequences or so difficult to unmake.  And yet, by and large, executives make poor promotion and staffing decisions.  By all accounts, their batting average is no better than .333; at most one third of such decisions turn our right, one third are minimal effective; and one third are outright failures.”

Frank Schmidt and John Hunter in their work “The Validity and Utility of Selection Methods in Personnel Psychology: Practical and Theoretical Implications of 85 Years of Research Findings”, Psychological Bulletin 1998, applied the following validity scores to selected assessment methods:

• Work Sample Tests .54
• Mental Ability Tests .54
• Structured Interviews .51
• Job Knowledge Tests .48
• Training and Experience (Behavioral) .45
• Unstructured Interviews .38
• Reference Checks .26
• Job Experience (Years) .18
• Training and Experience.11
• (Points) Years of Education 1.00

In more recent studies, the data is again validated. Bradford Smart in his book Top grading: How leading Companies Win By Hiring, Coaching and Keeping the Best People. (1999 and 2005) shares success rates of companies AFTER most of them received coaching on how to hire successfully.  Smart writes that in a survey of 100 CEOs in major US companies 52% reported having A-players on their executive team.