How Slack Got Ahead in Diversity

Slack has been outperforming other Silicon Valley companies when it comes to minority employees, according to the organization’s latest diversity report.

Several people sitting on green couches with laptops
Slack's Vancouver office (Slack)

Last week, Slack, the company whose popular, plaid-themed messaging app has simplified office communications and introduced the custom-fox emoji into our daily routines, quietly released its 2017 diversity report. Such reports, which list statistics such as the percentage of women in management and underrepresented minorities in technical jobs, have become something of an annual rite of passage among Silicon Valley tech companies. As public concern about gender and racial inequities in tech has grown, companies have begun, over the past several years, to share figures.

Slack has been outperforming other Silicon Valley companies, and its current numbers show that the trend has continued. At Google, Facebook, and Microsoft, women hold between 19 percent and 28 percent of leadership positions and between 19 percent and 20 percent of technical roles, according to those companies’ most recent figures. At Slack, women make up 31 percent of leaders and hold 34 percent of technical roles. Also, in Slack’s U.S. workforce, percentages of underrepresented minorities (including black or African-American, Hispanic or Latino, or American Indian or Alaskan employees), are, in some cases, triple that of peer companies. At Google, Facebook, and Microsoft, underrepresented minorities hold between 4 and almost 8 percent of technical roles and make up less than 11 percent of all employees. At Slack, by contrast, underrepresented minorities make up almost 13 percent of technical roles and roughly 13 percent of all employees; they also make up 6 percent of leadership. The number of Hispanic women at the company has more than doubled since last year. The number of Hispanic men more than quadrupled.

What’s notable about this is that Slack has achieved it without a designated “head of diversity,” a role that has become ubiquitous at tech companies—Google, Facebook, and Microsoft each have one—and might soon become more so; the lobbying group that represents tech companies in Washington, the Internet Association, hired its own director of diversity and inclusion last week to focus on “diversity, inclusion, and workforce-related policies,” after members of the Congressional Black Caucus pressed the organization on the lack of diversity at big tech companies. While studies by the Harvard University professor Frank Dobbin, and colleagues, suggest having someone overseeing diversity efforts can increase the numbers of underrepresented groups in management, other measures, such as mentoring programs and transparency around what it takes to be promoted, are also important; a diversity chief alone may not be enough to make much of a difference. At Slack, the absence of a single diversity leader seems to signal that diversity and inclusion aren’t standalone missions, to be shunted off to a designated specialist, but are rather intertwined with the company's overall strategy. As the CEO, Stewart Butterfield, has said, he wants these efforts to be something “everyone is engaged in.” Indeed, as the research by Dobbin and colleagues shows, involving employees in diversity policies leads to greater results.

I’ve been speaking with employees at Slack for the last couple of years, while researching a book about mitigating bias, and have witnessed an all-hands effort, organized around several specific policies, to create a fairer and more inclusive workplace. These efforts began with the company’s launch in 2014, and have only accelerated. “All of us believe it’s our responsibility,” Julia Grace, Slack’s senior director of infrastructure engineering, told me.

For one thing, the company has, since 2015, proactively sought out candidates from outside traditional programmer pipelines like Stanford and MIT, recruiting through all-women’s coding camps like Hackbright, as well as programs that focus on training black and Latino programmers such as Code2040. Recruiters are trained to look at skills rather than a candidate’s university pedigree. In 2015, Slack worked with Textio, a company that analyzes job descriptions to ensure they appeal to the widest possible audience. (Slack’s job descriptions feature phrases like “care deeply” and “lasting relationships,” which statistically draw more applications from women. Microsoft’s, by contrast, feature words like “insatiably” and “competing.” Amazon’s keywords: “maniacal” and “wickedly.")

The company has also worked to eliminate opportunities for bias to creep into its hiring process. The “whiteboard interview,” for instance, is a classic part of software hiring in which candidates are asked to solve a coding problem in real time. But tracing one’s thought process with a dry-erase marker in front of a live, skeptical audience can create extra stressors for people from underrepresented groups. Interpersonal phenomena like stereotype threat, in which people from stigmatized groups spend mental energy grappling with negative stereotypes about those groups, can lead women and minorities with the same skills to perform more poorly.

So, from the beginning, Slack forwent whiteboard interviews in favor of a blind code review—modeled on the blind auditions that orchestras hold—in which candidates are given a problem to complete at home. All personal identifiers are wiped from each candidate’s homework, which is then evaluated against a rigorous checklist. Not only does this help eliminate stereotype threat, but it assures candidates they’ll be judged fairly. When it became clear, last year, that this approach presented additional challenges for candidates who cared for children and didn’t have dedicated time for homework, the company shifted gears again. Candidates now have the option to do the assignment in the office if they prefer. “It’s a huge competitive advantage to be empathetic,” Grace told me. “Candidates know that the company is excited to accommodate them.”

In 2016, Slack also revamped how it interviews candidates. Bias has the potential to wreak havoc on that process: Interviewers may inadvertently favor candidates who resemble themselves, and if criteria for a job are ambiguous, interviewers may mentally rejigger those criteria to fit whatever a favored candidate has. The technical term for this is “redefining merit,” and it’s a classic manifestation of bias. (In one study, people evaluating candidates for police chiefs were asked whether education or experience were more important for the job. When the male candidate had more education, they said education was more important. When the female candidate had more education, they preferred experience.)

So a team at Slack rebuilt the interview process. For each role, the team determined what characteristics and skills a successful candidate should have—communication skills, say, or capacity for teamwork. Then, for each of these, they defined what information they needed to assess those skills, and then devised a list of behavioral questions expressly aimed at sussing out that information, questions like “Tell me about a stressful situation, and how did it go?” or “Tell me about a change to your code base.” Each candidate now faces the same set of questions. “If you ask every candidate the same question,” Grace told me, “you start to see what a good answer looks like.”

Finally, interviewers were asked to do mock interviews with existing employees, the way doctors practice on fake patients. The interviewers themselves became more skilled—and less likely to introduce biases that could filter out good candidates.

This approach, in aggregate, seems to be working: Women in technical roles, for instance, are up almost 5 percentage points from last year. “Folks on my team very regularly talk about how this is the most diverse company that they've ever worked at,” Grace told me.

Slack’s numbers aren't perfect. While Slack’s technical population is 13 percent underrepresented minorities, black and Hispanic students make up 22 percent of computer science majors in the United States. Black and Hispanic women are scarce at Slack, making up only 6 percent of U.S. employees. Erica Baker, an African-American engineer who has been a vocal advocate for more inclusion in tech, said in 2016 that she was pushing Slack to publish figures on its retention rates and be more transparent about salaries, in an effort to broaden the company’s focus from simply hiring more underrepresented minorities to helping them succeed and feel included there. Baker left the company last year, implying that she experienced difficulty moving up as quickly as she would have liked. Slack’s executives are 100 percent white or Asian. Only two of its eight top executives are women. “We exist in the actual world—if we all agree that this world has some systemic issues, and it’s sexist and it’s racist—that’s not going to stop when people walk into our office,” Butterfield has said, acknowledging the work that has yet to be done. New efforts include working on curricula with Code2040 to ensure workplace success for its trainees, and developing ally training with the Transgender Law Project.

Slack is still ahead of its peers. Carly Robinson, a software engineer hired through Hackbright, told me, "I'd been preparing myself for all the stereotypes of tech. But I haven't felt that way at Slack.” Some engineers cite growth as an impediment to hiring with diversity in mind—it takes time they just don’t have. Slack, though, has continued to improve employee diversity while also growing rapidly: Since its last diversity report, a year ago, the number of U.S. employees has increased from 439 to 709. The company, Grace told me, sees growth as helping, not stymying, its diversity efforts: The company can learn quickly and make changes. And focusing on diversity from the very beginning, as Slack has done, has been an advantage: It's easier to build a diverse company when most employees have yet to be hired than fix it later.

All of these efforts may have a less obvious, but profound, effect. When a company puts intense effort into diversity and inclusion, it serves as a signal to employees that the company takes it seriously, and that, in itself, can have a positive effect on things like employee morale or feelings of inclusion. If trying to improve diversity and inclusion is the norm, even if the results aren't perfect, it confirms a commitment and concern about these issues. (Joseul Musambaghani, a Congolese-born former intern at Slack, said that Butterfield circulating a memo about police shootings in Louisiana and Minneapolis made him feel supported.) “For most of my career,” Grace told me, “There were very few other women in the room, and it's so refreshing to have such a large critical mass of other women in the room. For a lot of the men that I work with, this is the first place where maybe it wasn't just all men.”

We want to hear from you. Please email your response to