More than 40 years after women began pouring into the workplace, only a handful have made it all the way to the top of corporate America. Why are women CEOs so rare? The percentage of chief executives of Fortune 500 companies who are women just passed 6 percent, creeping up (and occasionally dropping back) at a glacial pace. Why don’t more women get that No. 1 job?

The impact of gender is hard to pin down decisively. But after years of biting their tongues, believing their ranks would swell if they simply worked hard, many senior women in business are concluding that the barriers are more deeply rooted and persistent than they wanted to believe, according to interviews with nearly two dozen chief executives, would-be chief executives, headhunters, business school deans and human resources professionals.

What they say: Women are often seen as dependable, less often as visionary. Women tend to be less comfortable with self-promotion — and more likely to be criticized when they do grab the spotlight. Men remain threatened by assertive women. Most women are not socialized to be unapologetically competitive. Some women get discouraged and drop out along the way. And many are disproportionately penalized for stumbles.

“For years I thought it was a pipeline question,” said Julie Daum, who has led efforts to recruit women for corporate boards at Spencer Stuart. “But it’s not — I’ve been watching the pipeline for 25 years. There is real bias, and without the ability to shine a light on it and really measure it, I don’t think anything’s going to change. Ultimately at the top of an organization there are fewer and fewer spots, and if you can eliminate an entire class of people, it makes it easier.”

Jan Fields worked her way from crew member at a McDonald’s restaurant to become president of McDonald’s USA, the No. 2 position at the company. She was fired in 2012, blamed for the first monthly drop in profits since 2003 during a strategic push for higher prices. From her perspective, she was making bold changes necessary for the company’s survival; McDonald’s has struggled in recent years amid increasing consumer consciousness about health.

She’s blunt about the life of a woman near the top.

“You’re the only woman,” she said. “It’s very lonely. I was at a high level playing in a golf foursome with all high-level men. One said, ‘I didn’t know you knew how to play.’ I said, ‘You never asked me.’ I never drank with them. I never tried to be one of the guys. I spent more energy on performance.”

In the end, she said, she won over many of the men. “The men along the way, they were extremely jealous and competitive,” she said. “It didn’t really last that long because they saw my production, and when they did start to work for me, they realized, ‘She was not that bad.’ ”

Like many women who became senior executives, she said she rose fastest and most smoothly when she was measured by the straightforward metric of profits. “It’s really all about money,” she said. “I always had to do better than anybody else to be considered equal. I ran great restaurants, had great profits and had the most successful people working for me.”

One handicap to becoming the chief executive, she said, was her own choice not to work overseas. “I thought so many of the countries we were going into were so against women,” she said. “I thought, I don’t need that.”

But after three years in the No. 2 spot, she and her boss disagreed about strategy. She pushed hard for changes, as she said many women in her place have done. “That’s how come I’m gone,” she said.

“I got a guy his C-suite job,” she recalled. “I’m sitting there at the C-suite table and he takes a massive swipe at me on my business: ‘She’s not doing this right.’ I go down the hall, and I go to my friend and say, ‘What the hell just happened?’ And she said, ‘Did you forget the boys play a 24/7 game of dodge ball? You just walked into the gym. You whip the ball, and if it happens to knock somebody on the head, so what?’ And my husband said, ‘Why the hell did you help him get his job two years ago?’ ”

Her turning point came when she was outmaneuvered by male colleagues during a corporate reorganization. Believing she was not going to rise further, she asked for an exit package.

Looking back, she is convinced that being a woman hurt her. “I rewrote the entire strategy for the company, doubled its share price,” she said. “We had a little bit of a dip. All of the guys had missed their numbers more. There’s a guy positioning himself as the successor. He hasn’t made his number in seven years. He’s tall and good looking and hangs around the right circles.”

She drew an unwelcome conclusion. “Women are prey,” she said. “They can smell it in the water, that women are not going to play the same game. Those men think, ‘If I kick her, she’s not going to kick back, but the men will. So I’ll go after her.’ It’s keeping women in their place. I truly believe that.”

Many women, accomplished as they are, don’t feel the same sense of innate confidence as their male peers. Gerri Elliott, a former senior executive at Juniper Networks (who said she did not personally encounter bias), recounts a story related by a colleague: A presenter asked a group of men and women whether anyone had expertise in breast-feeding. A man raised his hand. He had watched his wife for three months. The women in the crowd, mothers among them, didn’t come forward as experts.

Shelley Diamond rose to chief client officer at Young & Rubicam after running its New York office and leading several key worldwide accounts. Early in her career, she said, “My biggest Achilles’ heel was my own confidence in myself and my ability to accomplish a task that seemed giant and daunting and scary.”

But she and other women describe a culture in which men sometimes feel hesitant to give women honest but harsh feedback, which can be necessary for them to ascend, because they fear women may react emotionally.

For her part, Mrs. Clinton is writing a book and speaking out more acidly than she allowed herself on the campaign trail. “Certainly, misogyny played a role” in her defeat, she told a rapt, partisan crowd at the Women in the World summit meeting in April. She described what she saw as the thought bubble among some voters for President Trump: “He looks like somebody who’s been president before.”

The fury and revulsion aimed at Mrs. Clinton — as well as the more open misogyny in some quarters in the wake of the election — has led many women to question whether they’ve underestimated a visceral recoil against women taking power in any arena.

Many fear they already know the answer.