This is the first part of a three-part excerpt. It is an edited version of Chapter 3 of Maddy Dychtwald's book, Influence: How Women's Soaring Economic Power Will Transform Our World for the Better. (Voice, Hyperion) 

In businesses of all sizes, women today are finding new ways of working that make more sense for their lives (and for the lives of their life partners and children and extended families as well). Business as usual, in a workplace designed by men, for men, with at-home spouses, just isn't working for a huge number of women. Frankly, it hasn't been working well for a lot of men, either.

"The current work model is the old model," says Karen Sumberg, vice president of the Center for Work-Life Policy. "It addresses a white man with a stay-at-home wife. But that person represents an increasingly small portion of the work force. White men are becoming the minority in the workplace, which is increasingly populated with women and men of different cultures and ethnicities." The American work force is vastly different than it was 50 years ago, or even a decade ago. In 1950, 30 percent of the U.S. work force was women. Today, it's about half women. In the 1950s, a minority of mothers worked. Today, 70 percent do.

But most companies are still run by men with spouses at home. In the United States, 85 percent of corporate officers at Fortune 500 companies are men. Women make up just 26.7 percent of all general and operations managers. Globally, senior male executives (75 percent of them) usually have a stay-at-home partner, while 74 percent of senior women executives have a partner who works full time.

It's no wonder the old rules and paradigms of most workplaces don't work well for many women, especially mothers. Many workplaces are outright hostile to family needs. "My twins were born very prematurely. My son weighed less than 2 pounds," says Kathleen Hall, now general manager of consumer marketing at Microsoft. Her employer at the time, an advertising agency, showed little respect for family needs. "I was on maternity leave when they said, 'You have to come back, we have a huge pitch.' I said, 'You know I have two kids in intensive care. What are you people thinking?' " Later in her career, at a financial services firm, she again encountered hostility when she had to take six weeks off to care for her 11-year-old son's sudden severe health problems. "Even when you have a track record of high performance, you can still encounter little or no tolerance for family needs."

If a sensible response to family needs is that hard to come by for a high-powered executive like Hall, just imagine how family needs are treated for the vast majority of American workers. Hall's case is just one, glaringly clear example of the mismatch between the real work force -- full of working moms, working dads, older people and many other nontraditional workers with full lives outside the office -- and the mythical corporate work force that doesn't bat an eye at 70-hour weeks, every week, for years on end.

When it comes to today's work force, perception does not fit reality.

What do you do when something doesn't fit? You alter it, or leave it and find something else that works better. For many women in the United States, the latter choice has been more alluring. "There's an ongoing parade of women moving out of corporations who say, 'This is too soul crushing,' " says Nell Merlino, founder, president and CEO of Count Me In for Women's Economic Independence, a nonprofit organization that, in 2005, launched an initiative called Make Mine a Million $ Business to boost women-owned businesses over the million-dollar sales mark. Every day, more than 400 U.S. women start their own companies -- twice the rate at which men do so. The number of women-owned firms grew by 19.8 percent between 1997 and 2002, then leaped a whopping 55 percent after 2002. Today, 10.1 million firms are owned by women. These businesses employ more than 13 million people, and they generated $1.9 trillion in sales in 2008.

The growth -- in numbers and in revenue -- of women-owned businesses represents a massive change. But what's even more important is the way women are writing their own rules for the workplace and changing paradigms along the way -- specifically, upending our ideas about when, where and how work gets done -- to fit new realities about who (men or women, parents or single people) is doing that work.

Next: Shape the Work World You Want