IBM allegedly targeted older American workers with layoffs, firings and forced retirement to systematically replace them with younger, cheaper millennials and overseas workers, according to a new report.

In the past five years, the investigation found more than 20,000 IBM workers -- about 60 percent of its estimated total U.S. job cuts in that period -- were over the age of 40. IBM, which still employs 400,000 people worldwide, flouted domestic laws and regulations protecting older workers from age discrimination by not providing information on why they were fired, required them to sign away the right to sue IBM and converted job cuts into retirements to avoid public disclosure requirements, alleged the report published Thursday by ProPublica and Mother Jones.

"We are proud of our company and our employees' ability to reinvent themselves era after era, while always complying with the law," said IBM spokesperson Edward Barbini in the report. "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."

IBM did not immediately respond to a request for comment to this news organization regarding the report.

ProPublica and Mother Jones uncovered internal documents that allege IBM was aggressively looking into hiring a younger workforce. In one 2014 internal presentational slide, it read CAMS -- an IBM moniker for new emerging technologies like cloud services, mobile, big data and social media -- "are driven by millennial traits." In the same presentation, baby boomers were depicted as "more dubious" of analytics, placing "less stock in the advantages data offers" and less "motivated to consult their colleagues or get their buy in," according to the report.

Internal spreadsheets that evaluated IBM workers' performance and listed workers on the chopping block alleged IBM's job-elimination strategy skewed toward older workers, according to the report. One spreadsheet from 2016 created to start the process of layoffs, job outsourcing and replacement had more than 400 full-time IBM workers listed; 90 percent of the workers were over the age of 40, according to the report.

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Another spreadsheet from 2014, with more than 600 IBM workers listed, evaluated job performance -- the ones with no or low scores were more susceptible to layoffs. ProPublica and Mother Jones found employees with no points on their job performance averaged around 30 years of employment with IBM. However, in the same spreadsheet, the vast majority of the employees with no points had a rating from their superiors who said they were good enough to stay on in their current job or in a promoted job, according to the report.

IBM allegedly skirted around the issue of publicly disclosing its corporate layoffs after 2014, a regulation in the Age Discrimination in Employment Act, says the report. Before 2014, IBM provided two lists -- one of those who were laid off and their positions and ages, but not names, and another of those who were staying on -- to those who were laid off. But after 2014, IBM stopped providing the lists, saying the lists "infringed on employee privacy".

To nullify the necessity of public disclosure of its layoffs, IBM allegedly chose in a new 2014 company layoff policy to drop age from one of its many waived categories of what laid-off workers receiving severance could take to court. In short, former IBM workers could technically sue IBM for age discrimination, according to the report. But the layoff policy also had employees waive their rights to take cases to court and the right to join other workers to make a case -- limiting them to a confidential and private arbitration process to pursue age-discrimination cases.

With no public disclosures of layoffs, IBM workers had to resort to banding together online in Facebook groups under names like "Watching IBM" or "Geographically Undesirable IBM Marketers," according to a separate post by ProPublica explaining how it began reporting on this investigation.

Some IBM employees over the age of 40 allege IBM offered either an early, voluntary retirement or a layoff, leaving no choice but to accept a retirement package. One employee who worked remotely retired after being given 30 days to decide to move 2,600 miles to work on an IBM campus.

Another employee lost his job at IBM but was signed on as a subcontractor with a lower wage and no benefits such as health care two weeks later. IBM allegedly contracted ex-employees dozens of times, according to the report.