"[O]ne recent study found that executive coaching produced about three times as much improvement in overall performance as other management development techniques."
Vaulting over the performance bar: The power of Executive Coaching
HR Outlook, Vol 1, Issue 3, page 4, 2000
Drake Beam Morin

"[M]ore than 70% of the respondents to a survey of HR professionals believed that coaching is actually more effective than training courses as a means of changing behavior and improving the performance of senior executives and high-flyers."
When executive coaching fails to deliver: Is it time to kick sporting metaphors into touch?
Development and Learning in Organizations: An International Journal (formerly Training Strategies for Tomorrow), Vol 17, Number 2, pages 17-20, 2003

"[In a survey of forty-eight executives who had received coaching] there was almost unanimous agreement that having a coach helped in all aspects of life and enhanced both business and personal relationships."
The executive coach: helper or healer?
Training, page 34, March 1998
Filipczak, Bob

In a Manchester study of one hundred executives who had completed coaching: "The average return on investment [ROI] was nearly 5.7 times the initial investment."
The Ins And Outs of Executive Coaching
Training, pages 36-41, May 2004
Johnson, Heather

"[The ICF's] global membership has soared from about 1,500 in 1999 to almost 7,000 today. The coaching market is now worth around $1 billion worldwide, a number that Harvard Business School expects to double in the next two years."
Corporate therapy
The Economist, page 61, November 15th, 2003