One of the best explanations for the triumph of a “solution shop” like McKinsey was co-written by the late Clayton Christensen of Harvard Business School in 2013. When hiring a management-consulting firm, he said, clients do not know what they are getting in advance, because they are looking for knowledge that they themselves lack. They cannot measure the results, either, because outside factors, such as the quality of execution, influence the outcome of the consultant’s recommendations.
