I do feel this is something that should be made illegal. In many countries it is a breach of your employment contract to diverge your pay, unionise, etc. Howeve

I do feel this is something that should be made illegal. In many countries it is a breach of your employment contract to diverge your pay, unionise, etc. However it is ok for employers to share data with each other, even if they don't have a business relationship other than keeping your wage down. It makes it hard to negotiate pay rises, change jobs, and get a fair market price for your wage. Doesn't feel fair to me.