Many companies are able to purchase previous employment salary data, which I believe Equifax sells directly: https://news.ycombinator.com/item?id=29834753
Here is a great read about the tools companies have to suppress your wage for anyone who wants to be a little angry: https://www.pave.com/blog-posts/acquiring-option-impact-and-...
> At Pave, we spent the last two years building out a suite of 40+ integrations with HRIS, payroll, and equity management systems that connect directly with the source of truth for compensation data. We are thrilled to bring this technology to the Option Impact customer base and ensure that our combined customers will never have to fill out a manual survey again while gaining access to a persistent real-time network of compensation data.
[pdf] https://advisor.morganstanley.com/the-hamilton-retirement-pl...
> Option Impact is free to eligible and participating companies through our give-to-get model.
So if I understand correctly, almost all of our employers are providing our real time compensation data to an entity that then allows all other participant companies to graph and query.
I find it outrageous that my employer could tell my compensation data to other companies, while simultaneously we live in a culture of "we shouldn't talk about compensation."