Every year, Len and Cal — two thoughtful partners in a law firm — have to evaluate a handful of direct reports and assign them end-of-year bonuses. Both Len and Cal take this responsibility very seriously, as their decisions are consequential for their subordinates and their firm. In most respects the influences on Len’s and Cal’s decision making appear similar: they both follow the same company policies and norms, and they both have similar backgrounds and pedigrees. Yet the outcomes of their bonus decisions are remarkably different: over the years, Len’s female employees have consistently received a greater share of the bonus pool, compared with Cal’s female employees.

One difference between Len and Cal is that Len is liberal and Cal is conservative. But why would their political views matter when they allocate bonuses to their male and female reports?

Len and Cal are fictional characters, but they represent the findings of our research (forthcoming in the Academy of Management Journal) on one large U.S. corporate law firm, which indicates that the political values of managers can be a powerful influence on how they allocate bonuses.

A large body of research has uncovered how political values shape decisions in our day-to-day lives, from what we buy to where we live to what types of leisure activities we take up. Politics and work, however, have been viewed as distinct spheres of life, making it challenging to unpack the extent to which these values seep into decision-making at the office. After all, managers often do not disclose their political leanings at work.

To overcome this challenge, we gathered publicly available donations data from the Federal Election Commission. We determined the political ideology of 119 managers working within our sample law firm by finding how each person contributed to either Republican or Democratic campaigns from 1990 to 2014. We looked at how much, how often, and for how long they contributed to each party. In this way, we identified where on the liberal-versus-conservative continuum each partner fell. For example, a partner who donated 80% to Republicans and 20% to Democrats would be coded as conservative, but not as conservative as a partner who donated 100% to Republicans. (In our sample, there were more liberal than conservative partners in the firm, and there were more male than female associates, although at low levels of seniority, the numbers were close to equal.)

Do Political Donations Really Tell You How Liberal Or Conservative Someone Is? The methodology we used in this study is based on a validated technique used by M.K. Chin, Donald C. Hambrick, and Linda K. Trevino in a 2013 paper published by Administrative Science Quarterly. They developed the technique and used it to estimate how liberal and conservative CEOs were, giving each a score based on the same methods we’re using here. To validate this method, they then asked a different group of executives to take a survey identifying how liberal or conservative they were on a seven-point scale (Very Conservative, Moderately Conservative, Slightly Conservative, Middle of Political Spectrum, Slightly Liberal, Moderately Liberal, Very Liberal). They then calculated scores for those executives based on their political donations — just as they did with the CEOs. Their work showed a .51 positive correlation between the index and self-identified political ideology. As a reminder, -1 shows a negative correlation, 0 is no correlation, and +1 is perfect correlation; typically, any correlation above .4 between a single-item survey and a composite index is considered valid. So, while not perfectly precise, this method has been found to be a moderate indicator of political ideology.

We then used the data we had collected to see if there was an association between a manager’s political values and how they allocated bonuses to their male and female direct reports. As in most professional service firms, supervising managers in this firm evaluate their direct reports, and those evaluations feed directly into reward and promotion decisions. To capture the end result of this process, we gathered the annual bonus allocation decisions for all the firm’s associates (359 in total) from 2002 to 2007, and linked those to the partners supervising them each year.

What we found

Our findings revealed a gender gap in bonuses given to men and women that was minimal for partners at the liberal end of the ideological spectrum but much larger at the conservative end. Under the most conservative managers (those who only donated to Republican campaigns), men received nearly $5,000 more, on average, in annual bonuses than women. Importantly, these findings could not be explained away by differences in associates’ backgrounds or work efforts, including their billable hours.

This effect was even greater for law firm associates who had more seniority and worked for conservative partners. Under the most conservative managers, experienced men received over $15,000 more in annual bonuses, on average, than comparably experienced women. In contrast, the gap was smaller for newer employees. It’s worth noting that we found these effects even after accounting for the increase in overall bonus size that comes with seniority. And under most liberal managers, the associate’s gender did not play a statistically significant role regardless of seniority.

To account for other factors that might influence these findings, we ran a number of controls to see if differences in the backgrounds or expertise of partners and associates were driving this gender gap. We found that they were not. We also ran numerous robustness checks to account for alternative explanations, such as individual differences in human capital.

Why does this happen?

Our findings raise many questions about why managers’ political values would shape how they allocate rewards to men and women. Because we could not directly measure their psychological processes, we drew on prior research in sociology and political psychology to interpret these differences between liberal and conservative managers’ decisions.

Although firm structures and policies can be designed to limit gender inequality, in many professional services jobs the onus of making critical decisions about bonuses and promotions falls on the shoulders of managers and team leaders. Since there is often a great deal of uncertainty about how work should be evaluated in these fields, managers may fall back on values and beliefs that shape how they perceive and interpret information about workers. So, basically, there is room for personal beliefs to play some role in their decision making — and this is where personal political ideology can come in.

Recent research has shown that managerial discretion is linked to bias in worker rewards — both men and women managers have been found to favor men in their decision-making around bonuses, and the presence of this bias helps explain the persistent gender inequality in pay we still see today. However, managers vary in how much they perpetuate this bias, depending on their own personal values and beliefs. So supervisor beliefs about social change and inequality in society – primary elements in whether one is ideologically liberal or conservative — can affect decisions about performance and bonuses.

We theorized that liberal and conservative supervisors rely on different heuristics when they make reward decisions. Indeed, a vast body of research in this domain shows systematic differences in how liberals versus conservatives think about society; for example, liberals are found to be concerned about systems and norms disadvantaging certain groups in society, including women, and they may be more interested in rectifying these than in preserving the male-dominated status quo. Conservatives, on the other hand, are found to value aspects of those systems and norms that incentivize and reward individual contributions, and they tend to be more accepting of differences in outcomes, including between women and men, as reflecting varied motivations and capabilities. So in our study context, where performance is more ambiguous and evaluation requires more subjectivity, ideology may influence decisions such that liberals may respond more favorably to female subordinates as a way to reject male-typed norms, and conservatives may respond more favorably to male subordinates as a way to maintain the status quo in a professional context that favors men.

This may help explain why we see a larger gap in bonuses as employees gain seniority. As they shift to more challenging and higher-level assignments, the ambiguity around their performance increases, driving managers to rely even more on their own discretion.

Of course, there may be other explanations we’re unable to rule out — we’re only beginning to measure how political leanings affect the workplace. Our findings are based on the study of one firm and may not generalize elsewhere – though they appear consistent with other recent research on the effects of political ideology on gender parity in law firms and large corporations.

But they could apply to many professional settings, where supervisors tend to lack objective performance indicators and rely more on subjective discretion in evaluating performance and allocating rewards. We’d expect that the impact of supervisor political values would decrease in settings involving routine work that can be largely captured through objective performance indicators.

Overall, our work suggests that professional firms may start to address gender pay inequality by increasing transparency on reward and promotion decisions for men and women.