Here’s the fourth and final criterion for making the Fortune Most Powerful Women List: social and cultural influence. It’s certainly more difficult to measure than revenues or profits, the health of a business, or even the arc of a woman leader’s career. But vast social and cultural influence is precisely why Oprah Winfrey ranks No. 8 on our list. Her company, Harpo, is privately held and nowhere near the size of what other MPWomen control (typically businesses with at least $6 billion in sales). But given Oprah’s media assets — O, The Oprah Magazine, her own TV show, and her interests in Dr. Phil, Rachael Ray, and more — you see why we say she’s more powerful even than some Fortune 500 CEOs, such as Sara Lee’s Brenda Barnes.
Click here to see video excerpts of a Most Powerful Women panel on leadership that we did in New York in May. The panel includes Ursula Burns, president of Xerox; Andrea Jung, CEO of Avon; and Ann Moore, CEO of Time Inc.