A study of the diversification records of 33 large U.S. companies from 1950 to 1986 shows that diversification — whether through acquisition, joint venture, or start-up — generally has not brought the competitive advantages or profitability expected. Portfolio management, restructuring, transferring skills, and sharing activities are four concepts of corporate strategy that companies most commonly use. Portfolio management no longer works very well in the United States because of its highly developed capital market. Restructuring is merely a stopgap measure that will not build shareholder value over the long term because it usually produces an unwieldy conglomerate. Companies have the best chance of being successful at diversification if they capitalize on the existing relationships between business units by having them transfer skills and share activities. McKinsey Award Winner.