This story is part of How We’ll Win in 2019, a year-long exploration of workplace gender equality. Read more stories here.

We’re used to the idea of a “systemic” gender pay gap where women’s work, historically undervalued, continues to be less well remunerated and respected than men’s. But to what extent is the wage gap a result of the choices that women themselves make, and how much of it is in their control?

In 2017, UBS, a wealth management firm and investment bank, wrote a report that tracked two hypothetical people, Jane and Joe, to see how their choices and other factors impacted their longterm financial health. UBS identified five factors that go into creating a situation in which women and men can end up with hugely different amounts of wealth in the latter part of life. The factors are: the existing pay gap, taking a short career break, flexible or part-time working, risk aversion, and life expectancy. Over the course of their lives, women and men can end up either well-cushioned for retirement or dependent on others, based on choices relating to these factors. “Jane,” in the UBS model, ends up with less money than she started out. “Joe” ends up with millions of dollars more.

Facebook COO Sheryl Sandberg ignited an ongoing debate about whether women “leaning in” more could mitigate the impact of some choices, or even sidestep them altogether. She has advocated for women demanding a seat at the table, outsourcing tasks, expecting their partners to take on equal domestic duties, and making greater ongoing commitments to their work, rather than committing less in the key mid-career years.

But this approach presupposes that it’s women’s actions that make the difference, rather than the structures within which they work. The fact is, no choice is made in a vacuum. The gap’s frustratingly slow narrowing is pushing institutions and individuals to examine the extent to which the “choices” open to women—from choosing a job in the first place to becoming the primary carer for young kids while her partner maintains a full-time career, to picking an investment strategy—are really choices at all.

Flexibility: Perk or trap?

Globally, women were paid 22% less than men in 2017, according to the Economic Policy Institute. Companies and governments increasingly want to close that gap, but the “extremely slow progress” towards equality means that, based on current trends, it will still take 202 years to achieve parity in economic participation and opportunity—a World Economic Forum estimate that increased last year because the world’s efforts bore so little fruit.

One of the biggest reasons the pay gap is so hard to close, particularly in industrialized countries—many of which have “equal pay for equal work” laws—is that women tend to choose to work part-time for stints during their careers, particularly after having children. Many suffer a penalty as a result that goes far beyond being paid for fewer hours, often effecting their longterm ability to earn. By the time her child is 20, the UK’s Institute for Fiscal Studies found, a woman will be earning 30% less than a similarly educated man, with the biggest reason being the likelihood that she will have spent time working part-time, missing out on career and pay advancement on the way.

Taking career breaks or working part-time to care for children or family members isn’t a choice for many women. Because men already tend to earn more than their female partners when kids arrive (or other caring needs manifest), the decision about whose salary to sacrifice by a cut in hours is often made by economic default. Added to that, social norms and company precedent can make it easier for women to reduce their hours than it would be—at least initially—for their male partner.

The US is one of the only countries in the world to mandate no leave for women who bear children, and mothers frequently return to work soon after having kids. But this commitment to continuity doesn’t make for a country with a particularly small gap. The US pay gap was 24.1% in 2016 according to Glassdoor, a company that monitors pay and equality. (Glassdoor also noted that when adjustments are made to create an “apples to apples” comparison, controlling for factors like role choice, age, seniority, and location, the gap shrank to 5.4%.)

Scandinavia, meanwhile, has made the most progress in closing its pay and opportunity gaps. With a pay gap of around 16%, Iceland is the country with best gender equality, according the WEF’s 2018 global gender gap report, with Norway, Sweden, and Finland following close behind. The region is also known for particularly long mandated leave for mothers and in many cases also for fathers. The comparison between Scandinavia and the US indicates that it’s not the choice to take a break that makes the difference: It’s the choice combined with a system that either penalizes or supports breaks.

Across developed economies, younger generations of workers, both men and women, have begun asking for more flexible working arrangements. There’s an opportunity in this for greater equality, as it becomes normal for either parent to flex their work around childcare. But it’s also possible that the ability to take work home or to remote locations will feed into an “always-on” culture that can be disastrous for home life and stress levels. Another interesting development is companies experimenting with shorter working weeks for all their staff. If a four-day week is standard across a firm, presumably no one will suffer discrimination because they don’t work five.

Appetite for risk

UBS notes that a big factor in women missing out economically is through choosing less high-return strategies for the money they do have. To what extent is risk aversion—when it comes to money or a career—a choice?

A number of studies have shown that women tend to be more risk-averse than men, and it can affect their earning potential. A 2009 examination of MBA students in the US found that lower levels of testosterone—the male hormone present in both genders, but usually higher in men—was associated with higher risk aversion, and that this manifested in less risky career choices. People with lower levels of testosterone (a cohort which included most of the women) were less likely to choose risky—and high-paying—finance careers. UBS’s 2017 “Jane & Joe” study also noted that women are less likely to make high-return, high-risk investment decisions.

But while the testosterone-study evidence suggests women may be biologically prone to choose safer, less highly rewarded careers and investments, more recent research published this year also found that risk aversion can be learnt, and suggested that growing up in a patriarchal culture teaches girls to be more risk averse than boys. Researchers from the University of Houston, Texas, and Fudan University, Shanghai, studied girls from two distinct social groups, the matrilineal Mosuo and the patriarchal Han, who attended the same school. When they arrived, Mosuo girls were more risk-taking than the boys from their own culture, and Han girls less risk-taking than Han boys—measured by choices made in a game that involved instant, small rewards or larger but less certain returns. Over time spent in one another’s company, however, the distinction shrank, with Mosuo girls apparently learning to be less risky and Han girls becoming less risk averse.

The implication of the study is that women are not necessarily biologically predisposed to lower risk (and lower returns), and nor are necessarily choosing it: They’re taught it by the way they’re raised and the cultures they live it. And that suggests they can change.

What we don’t choose—and what we do

In a longer life, the results of lower wages can be magnified. Women tend to live longer than men, meaning they have to sustain themselves financially for longer—a difference that, UBS notes, can wipe out more of what they’ve saved. Life expectancies certainly aren’t a choice, but there is some evidence that the gender life expectancy gap is closing due to factors including lower alcohol and tobacco use and better treatment for heart disease.

This year, UBS surveyed married, high-net-worth women and discovered that the majority deferred long term financial management decisions to their male partner. The finding suggests that, while men might be guilty of insisting on taking the financial reins in some cases, women are also complicit in relinquishing them, and UBS is advising women to work towards equal administration of their assets. When it comes to a whole career, the wealth manager says, women can counteract some of the disadvantages of being paid less by “disciplined” investments and better understanding the relationship between risk and return—actual choices over which they can exercise control.

Choices do indeed play into the gender pay gap. But many of them are based on systemic biases from which it’s hard, for people of any gender, to break free.

This story is part of How We’ll Win in 2019, a year-long exploration of workplace gender equality. Read more stories here.

Correction:An earlier version of this article mistakenly cited Glassdoor’s US salary figures instead of overall pay gap figures.