Whole Foods, which is owned by Amazon, is using a heat map to track stores that may be at risk of unionization, according to report from Business Insider.

The heat map apparently uses more than two dozen different metrics to track which Whole Foods stores may unionize. The heat map focuses on monitoring three main areas: “external risks,” “store risks,” and “team member sentiment,” according to Business Insider.

Here are some examples of “external risks,” reports Business Insider:

Some of the factors that contribute to external risk scores include local union membership size; distance in miles between the store and the closest union; number of charges filed with the National Labor Relations Board alleging labor-law violations; and a “labor incident tracker,” which logs incidents related to organizing and union activity.

Other external factors include the percentage of families within the store’s zip code that fall below the poverty line and the local unemployment rate.

Here are some examples of “store risks”:

Store-risk metrics include average store compensation, average total store sales, and a “diversity index” that represents the racial and ethnic diversity of every store. Stores at higher risk of unionizing have lower diversity and lower employee compensation, as well as higher total store sales and higher rates of workers’ compensation claims, according to the documents.

And here are some examples of how “team member sentiment” is tracked:

The “sentiment” data is pulled from internal employee surveys and “is likely to be the first score to improve based on your efforts.”

These measures assess employees’ feedback on the quality and safety of their work environment and whether they feel supported and respected, among other things. External risks include things the distance between that Whole Foods store and the closest union, charges filed with the National Labor Relations Board.

Amazon has resisted Whole Foods unionization efforts before — in 2018, the company sent a 45-minute anti-union training video to Whole Foods team leaders that was obtained by Gizmodo. “Throughout, the video claims Amazon prefers a ‘direct management’ structure where employees can bring grievances to their bosses individually, rather than union representation,” according to Gizmodo.

Whole Foods used similar language about direct management in a statement to Business Insider, which it also shared with The Verge. “Whole Foods Market recognizes the rights of our Team Members to decide whether union representation is right for them,” Whole Foods said in the statement. “We agree with the overwhelming majority of our Team Members that a direct relationship with Whole Foods Market and its leadership, where Team Members have open lines of communication and every individual is empowered to share feedback directly with their team leaders, is best.”

Amazon has not replied to a request for comment from The Verge.

Amazon has a history of aggressively combating unionization efforts, and its anti-labor stance has also come to light due to recent organizing efforts by warehouse employees to protest Amazon’s handling of worker safety during the COVID-19 pandemic. In late March, Amazon fired a warehouse worker named Chris Smalls who organized a walkout in New York City, claiming he violated COVID-19 safety instructions after coming into contact with a co-worker who tested positive for the virus.

However, Amazon executives later attacked Smalls on Twitter after Sen. Bernie Sanders (D-VT) criticized the company. Shortly after, notes from an Amazon executive meeting obtained by Vice News revealed a plan to publicly smear the worker in an effort to discredit broader labor movements within Amazon.

Update April 20th, 6:31PM ET: Whole Foods provided the same statement to The Verge that it provided to Business Insider.