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In the new book "The Firm: The Story of McKinsey and Its Secret Influence on American Business" (Simon & Schuster), award-winning financial journalist Duff McDonald provides an intimate and incisive behind-the-scenes history and analysis of this influential and enigmatic company, which helped invent what we think of as American—now global—capitalism. With unprecedented access to current and former McKinsey employees, McDonald for the first time tells the whole story of The Firm—a story that is inextricably tied to the dramatic and fluid story of American business itself in the twentieth century. The following is an excerpt from "The Firm":

Two minutes out of business school, Jamie Dimon decided to become a consultant. The experience left him unimpressed, and he has looked down on it since. "It's substitute management," he told me when I was deep into writing his biography. "A Good Housekeeping seal of approval. It's political, so if you make a decision, you can say, 'It's not my fault, it's their fault.' ... I think consultants can become a disease for corporations." Dimon, who went on to become the chairman and CEO of JPMorgan Chase and was hailed as an Olympian financier for steering the bank above Wall Street's 2008 humbling—only to be somewhat humbled himself four years later when its own trading caused more than $5 billion in losses—made one exception to his consultant rule. Most consulting engagements weren't worth the price paid, he said, but McKinsey—well, it was the real thing.

Four years later, the Republican candidate for president, once a consultant himself, was asked how he would reduce the size of government. "So I would have ... at least some structure that McKinsey would guide me to put in place," Mitt Romney told the editorial board of The Wall Street Journal. When his audience seemed surprised, he added, "I'm not kidding. I probably would bring in McKinsey." After almost a century in business, McKinsey can lay claim to the following incomplete list of accomplishments: Once before, well before Romney was running for the presidency, it remapped the power structure within the White House; it guided postwar Europe through a massive corporate reorganization; it helped invent the bar code; it revolutionized business schools; it even created the idea of budgeting as a management tool. Above all, McKinsey consultants have helped companies and governments create and maintain many of the corporate behaviors that have shaped the world in which we live. And in becoming an indispensable part of decision making at the highest levels, they have not only emerged as one of the great business success stories of our time but also helped invent what we think of as American capitalism and spread it to every corner of the world. The abstract, white-collar nature of modern business—the fact that the greatest value in our economy is now created by people sitting in air-conditioned skyscrapers and corporate parks who manipulate information—is a reality that McKinsey was instrumental in establishing, championing, and profiting from. The best evidence for McKinsey's expertise is the firm itself. It has followed its own advice into an enviable position of power and prestige.