When Slack reported statistics on staff diversity in September, the startup felt like it needed to explain why it was analyzing the gender and ethnic makeup of its meager 170 employees. Diversity reporting was a big company game, something tech giants like Facebook and Google did. A company less than 250 strong seems a little too small to yield any insight on diversity.

But for Slack, smallness was kind of the point. "It is relatively easy for us to move the lever a small bit right now to make a significant change in our trajectory," wrote CEO Stewart Butterfield and head of HR Anne Toth in a September blog post.

Now Slack is no longer quite so little: Valued at $2.8 billion, it was up to about 290 employees in December, and counts roughly 370 in its ranks at present. That rapid growth is why it is releasing a follow-up diversity report mere months after the last one. Data from the report is based on Slack's employee population as of December. 

Slack is still about as white as the tech industry at large, though it's a bit less male. In its latest report, the startup shares that 63 percent of its overall U.S. staff is white and 67 percent globally are white. Both in the U.S. and worldwide, women make up about 43 percent of staff.

By comparison, the tech industry at large was reportedly 64 percent white and 72 percent male in 2014.

Slack also reported the percentage of its staff that identifies as LGBTQ, a data point less frequently shared by tech companies.

Has the needle moved at Slack? It has. Here's a breakdown of how the most recent data compares to what Slack reported in September.

  • The percentage of engineers who are black has risen from 7 to 7.8 percent globally.
  • The overall percentage of black employees dropped from 4 to 3.4 percent in Slack's global staff.
  • Hispanic and Latino employees were not separately reported in the September survey. The latest survey pegs them at 4.1 percent globally and 5.3 percent among U.S. staff.
  • The percentage of employees globally who are Asian is 20 percent in the most recent data compared to 19 percent in September's report. 
  • The global percentage of the workforce that is white has dropped from 70 percent to about 67 percent. 
  • Employees identifying as women comprised 39 percent of Slack's global workforce in September and now comprise about 43 percent.
  • LGBTQ-identified employees comprised 10 percent of global staff in September. As of December, they comprised 13 percent.

The survey is voluntary, notes Slack's blog post about the data, and the structure of the most recent survey differs from the last one. Slack didn't report data specific to its U.S. workforce in September. There's a margin of error, to be sure.

"Because we are still small as companies go, every person we hire and every person who leaves can make a dramatic difference to our diversity data. For the most part, we appear to be harnessing our net growth in a positive way, but that could change," reads the post.

This post has been updated to reflect the change in percentage of black employees in overall global employee population, and the month from which data was pulled.