According to the data, job candidates of one political party were 40–75 percent more likely to be hired by someone of the same political party. For gender, the figure was 15–31 percent, and for race, 3 percent.
The discriminatory effect of political affiliation was stronger at smaller companies, where “personal interactions between owner and worker are likely more frequent,” write the researchers. Sorting along party lines was greatest among managers and weakest among low-level workers, they find, surmising that this is because owners and managers work more closely. When the owner of a company switched parties, the change showed up in a sudden shift in the politics of new hires.
Colonnelli, Neto, and Teso then conducted a field experiment, sending a set of fake résumés to 150 business owners and asking how interested they would be in hiring each candidate. To encourage truthful and well-considered responses, the researchers told the owners that after the experiment they would receive real résumés similar to those in which they expressed interest. The résumés were essentially identical to each other except for signals about an applicant’s political affiliation—introduced through cues such as volunteer experience with a particular campaign.
In the end, résumés of candidates whose partisanship aligned with an owner’s attracted a level of interest roughly 9 percent higher than those of candidates who were affiliated with a different party.
Finally, the researchers surveyed 1,000 workers and 1,000 owners at different companies. They explained their findings of political bias and then simply asked the participants what they thought drove the results. Owners and workers overwhelmingly cited discrimination, and 29 percent of business owners acknowledged outright that they took political views into account when hiring.
The upshot of this bias may ultimately hurt companies. Looking at the performance data for employees and companies, the researchers find that workers who identified with the same party as an owner tended to make more money and earn promotions more rapidly, even if they were less qualified than coworkers of a different party. And more generally, companies with a workforce more closely aligned with an owner’s politics appeared to grow more slowly than similar companies with a more politically diverse workforce, the analysis demonstrates.
Colonnelli suggests interpreting these outcomes “with a larger grain of salt” than usual because companies with a more politically aligned workforce could be different in many other ways than the researchers are able to observe in the data. That said, he adds, “it looks like there are real costs of partisanship in the workplace.”