The infusion of Series B funding brings the company’s total backing to $16.3 million. CEO and co-founder Didier Elzinga declined to discuss Culture Amp’s valuation in the latest round.

Culture Amp is part of a growing list of human resources software companies developing services that measure employee sentiment and worker productivity on an ongoing basis. The technology is sometimes described as “people analytics” because it gleans insights about worker attitudes and behavior using short surveys.

For example, online beauty product retailer Birchbox sends out team-level “pulse” surveys every quarter and supplement that information with longer questionnaires about specific strategic initiatives.

Culture Amp has tripled in size since its $6.3 million Series A funding in March 2015 by boosting its customer count to more than 500 companies, Elzinga told Fortune. The list includes Adobe, Airbnb, Box, Dropbox, Etsy, Pinterest, Slack, and Warby Parker.

“Having seen first-hand the positive impact of their data-driven approach at Dropbox, as well as their phenomenal growth among leading retail, hospitality, media and professional services clients, I am excited to be an investor and see Culture Amp’s impact on employee happiness,” said Index Ventures partner Ilya Fushman, in a statement.

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Culture Amp already measures sentiment on a regular basis for more than 60,000 employees at 150 fast-growing tech companies. That research correlates employee attitudes at top-performing companies and laggards with actual business performance.

One of the biggest trends highlighted in the latest data is the willingness of more organizations to seek input from employees across the entire company. “What that is saying is that every person is important,” Elzinga said. “People feel they can make a positive difference.”

Culture Amp currently operates out of Melbourne, Sydney, New York and San Francisco. Another office is planned for London this spring. It has 64 employees, but will probably end 2016 with at least double that payroll, according to Elzinga. His own background includes managing a visual effects startup and a stint with Tourism Australia.

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One of Culture Amp’s rivals in this space is Microsoft (MSFT), which snapped up another rising “people analytics” startup, VoloMetrix, in September for an undisclosed sum.

That company raised $17 million before being swallowed up, and has contracts with dozens of companies including Boeing, Facebook, Genentech, Qualcomm, Seagate, and Symantec. The VoloMetrix software is being rolled into Microsoft’s Delve service, which tracks employee productivity by analyzing schedules and email traffic, among other things.