So they're buying it from ADP?

Or getting it automatically from the employers in exchange for having access to it for new hires.

I doubt most employers would go for that, but I suppose it's possible. More importantly, though, it'd also be much harder than getting it from a payroll provider.

According to wiki they have 225 million employment records and according to The Work Number they are used by 82% of Fortune 500 employers.

Then they turn around and sell all that data while telling the participating companies what a wonderful service they are providing them by offloading this task from traditional HR.

It's crazy.

Oh, wow, that is crazy.

Prepare to be even more shocked. Here is a 'sample' of the EDR report you can request from The Work Number containing all the information that they have on you and may or may not be giving out (or selling to the highest bidder):

https://www.theworknumber.com/samples/The-Work-Number-Employ...

As you can see its much more than 'just' your salary. It includes (amongst other things):

Union Affiliation; Salary breakdown (Base, OT, Commission, Bonus); Dates of pay increases; Medical Insurance (coverage, Policy #, Provider name, Annual cost); Any Workers Comp claims; Breakdown of your paycheck (401k contribution, taxes payed, garnishments, etc)

Just imagine the national outrage if some employer was shown to be directly selling this information to someone about their own employees. Yet a third party is doing just that and many companies are complicit. It is absolutely outrageous!

'hmmm maybe I don't want to hire Joe Shmo, after all he did join a union in the past. He might try to unionize our plant'

'looks like Joe also has some garnishments, doesn't sound like someone we want on our team. Probably has a troubled past.'

'well looks like Joe made 70k last year, but a lot of that was from working OT. I think we can get away with offering him 60k and promising him a lot of OT "opportunities"'