Yes, it's concerning, but let's be realistic about this. I'm surprised HN readers are so surprised by this! On a scale of Room 641A (https://en.wikipedia.org/wiki/Room_641A) to carriers divulging location when you enter somebody's phone number (https://news.ycombinator.com/item?id=17081684), I'd say this is 2/10 bad. This really has nothing to do with employers colluding and trying to keep salaries low. Instead, it's just a way for businesses to verify your salary, given they have your SSN, DoB, and address.

First, it requires your SSN, date of birth, and home address. That a) means that prospective employers aren't able to view it (since you're not divulging your SSN in order to get an offer letter), and b) given these three pieces of information, requesting your salary is probably one of the least malicious things somebody could do. They could steal your identity, open up credit cards (some credit cards allow you to now get a virtual CC number before the card is shipped and confirmed), open up phone lines, SIM jack you, etc. Getting your salary data (given you have somebody's SSN, DoB, and home address) is likely one of the lowest things on the list.

Second, salary data is fairly public anyways. For example, if your company is of any reasonable size, they probably employ people on the H1B visa. Salary data is public already. Here, for example, is Airbnb's salary data: https://h1bdata.info/index.php?em=Airbnb&job=&city=&year=202....

Third, there are legitimate reasons why this system exists. If you're applying for a mortgage, how do you expect them to verify your salary? You can submit paystubs, but those can be faked. Same with bank statements. The only way for a bank to verify your salary is to actually call your employer. And if a bank calls your employer to verify your salary, and they have your DoB, SSN, and home address, it's pretty likely your employer is going to tell them anyways. Even if your employer only confirmed / denied (as opposed to providing a number), they could just repeatedly call and binary search it. (This probably wouldn't surprise the employer, since you might be getting quotes from multiple mortgage companies at once.) Given that mortgage companies, banks, and other finserv firms need to verify your income and employment history, it's not entirely unreasonable for a centralized database to exist, and for it to be guarded by what should be secret (SSN, DoB, address).

That said, the problem is that the US is too reliant on SSNs. If you prior on (the US treats SSNs as secret), being able to access salary data with it really isn't ridiculous.