I think this is a little off, in that the data isn't coming from the various government entities or at least isn't required to be provided. I know at least in California most of the info is gathered by third parties using FOIA requests. It's also not associated with a SSN and just typically gives the annual compensation with limited categories. The Work Number on the other hand gets paycheck level details. Considering the data would be useless without a unique identifier, SSN is sent with it. Using The Work Number data, you could see pay period granularity changes to their compensation.