Financial institutions have been employers of Women for decades: historically as tellers, secretaries, and junior administrative staff. In the 1980s, however, pioneering women began moving into management roles and into frontline business areas, such as investment banking. Today 47% of management and professional roles in American financial firms are occupied by women, according to the U.S. Bureau of Labor Statistics.

But this seemingly impressive statistic disguises an underlying lack of progress of gender equality in Financial Services. Women still aren’t making it to the top. An analysis that we conducted of disclosures made by 50 American financial services companies revealed that women occupy only 20% of executive committee roles and 22% of board positions. Only 12% of the chief executive officers of large U.S. financial firms are women.

Career progression analysis also shows that at each level, men are promoted at materially higher rates than women. Women are far more likely than men to leave the industry or to reduce their level of ambition just at the point in their careers when they need to make the effort to push on to the top. As a result, women’s prospects are significantly worse in financial services than in other sectors, A recent study conducted by our sister company Mercer discovered. One young female banker we interviewed for our 2016 report “Women in Financial Services” even told us, “I came into my career in financial services with aspirations to make it to the top. But now, five years into it, I am planning my escape.”

What explains the poor career prospects of women in financial services?

To find out, Oliver Wyman surveyed 850 financial services professionals from around the world (both men and women), interviewed over 100 senior female executives globally (C-suite and board members), and held focus groups with Millennial women working across a number of financial institutions in the U.S. Responses revealed a culture that has changed surprisingly little over the last 30 years. The overt sexism of earlier times may have been stamped out, but unconscious biases and gender-role expectations that disadvantage women have not.

This comes as a surprise to the many younger women entering the profession. Their female predecessors, entering the financial industry in the 1980s and 1990s, expected to deal with a certain amount of sexism. Given the general progress of gender equality, especially in education, most twentysomethings do not. Shifting from university to the financial industry, they experience a culture shock. As one Millennial banker we interviewed put it: “All of our senior leaders are older white males. They are the ones who set the culture that we experience every day, despite any programmatic efforts by the bank.”

The problem is not simply the tone or atmosphere of the workplace; it is the unstated ideas about what is required for success in the financial industry. An effective senior banker is (wrongly) imagined to be aggressive, dominating, transactional — characteristics that are stereotypically masculine and that are, as a matter of statistical fact, more commonly associated with men, as a recent study called “The Athena Doctrine” showed. Even our definition of leadership often follows stereotypical male characteristics. As a result, “we end up having to ‘masculinize’ our female traits,” one younger banker said.

The result is that women are implicitly held to a higher standard than their male colleagues. Proving yourself is harder for women. This helps to explain the very high quality of senior women in financial services; as one of our interviewees observed, “Some of the men at the top are extraordinary, but all of the women are.” As one senior woman we interviewed explained, “Firms are more willing to take risks on men. With a woman, she has to prove it first.” Consequently, many women lose confidence that they can succeed, and lower their ambitions or quit.

In short, women in financial services face a tougher career trade-off of higher costs and lower expected benefits. When the “deal” involved in committing themselves to getting to the top is worse for women, it is no wonder that fewer women take it. Many women must face a harsh reality: The cost of growing their career in financial services outweighs the potential benefits, taking into account the greater uncertainty and obstacles they face.

As one senior female banker we interviewed put it: “If [a woman] looks up and does not see any women at the top, she wonders if she will make it — if all of the sacrifices she will have to make will pay off.” (The ambition of male employees also falls off as they age, but it is later in their careers, in response to observed failure to progress rather than in expectation of it.)

Most financial firms are genuinely committed to improving gender balance among their senior executives. To that end, they have introduced a number of “women-friendly” programs, such as flexible hours, parental leave, and mentorship schemes. Helpful as they are, such measures do not fully address the problem, which also lies in the unconscious biases, expectations, and practices of organizational cultures, which have been created by predominantly male executives over decades. Getting middle and senior management to recognize their biases is the most important first step toward reforming the corporate culture that disadvantages women.

Efforts should also focus on supporting women at the inflection point by assisting firms with developing an understanding of the challenges and obstacles women face four to five years into their careers. At the same time, firms should adopt tools and practices to help the institution and the individual women manage this transition point, such as helping high-performing women better drive their careers by directing them toward roles and functions that have a direct path to senior leadership roles. Instituting a talent brokerage model in which hiring and promotion decisions are made not by individual executives but by diverse committees with representation from both the business and human resources is also important.

Senior executives cannot afford to sit back and take a passive approach, hoping for broader cultural change to permeate the financial industry. Consider that financial services firms are not just losing female talent to this problem; they are also missing out on female customers. Consider: According to a  2013 survey by CTI, over half of upper-income women — those earning $100,000 a year or more or possessing investable assets of at least half a million dollars — don’t have a financial advisor. One reasons for this is that they are not satisfied with the service they receive from the investment industry. This represents significant lost revenue for the industry — as much as $5 trillion in potential revenue in the U.S. alone, according to CTI.

For the sake of profits, innovation, and fairness, financial services firms must actively seek to change their corporate cultures. Otherwise, they will only continue to lose the talents of the financial industry’s many women, and the trust of their female clients.