Last month, ProPublica reported that over the past five years, IBM has targeted its older American employees for layoffs. The numbers are staggering: Since 2013, it’s estimated that IBM eliminated more than 20,000 employees ages 40 and older in the US.

Using public records, internal company documents, and a collection of stories from over 1,400 former IBM employees, the investigation pieced together how IBM went from dream employer in the 1980s to recent layoffs. How exactly does one of the country’s largest tech giants quietly push out so many older workers? Don’t we have laws to protect people at the end of their careers? Check out the video above for more.

In response to age discrimination claims, IBM spokesperson Ed Barbini has said: “We are proud of our company and our employees’ ability to reinvent themselves era after era, while always complying with the law. Our ability to do this is why we are the only tech company that has not only survived but thrived for more than 100 years.”

ProPublica hasn’t received further explanation or response from IBM in the weeks since its reporting on the company was published. But these layoffs haven’t ended. Members of a Facebook group, Watching IBM, have reported that IBM sent a wave of layoff notices in just the past few weeks.

If you know more, particularly about anything happening internally at the company, reach out here. This story makes up the seventh installment in Vox’s collaboration with ProPublica. You can find this video and all of Vox’s videos on YouTube. Subscribe and stay tuned for more from our partnership.