Are university salaries public information in Sweden? I am currently in the process of negotiating position both on the academic side and industry. I was told certain numbers on the spread of salaries for a specific position at a specific place, however I cannot locate the source of this information. 

So I am wondering whether or not salaries at a university are public information, specifically in Sweden. My understanding is that they are/should be, especially considering that even emails sent/received via university mail servers are covered as public information. 

On the other hand, labor unions like (such Sveriges Ingenjörer) typically give salary statistics is one of the major reasons why you should be a paying member. Why would I want to pay for information that is publicly available?

Follow-up: If salary information is indeed publicly available, then where can I find it; do I contact the institute of interest directly or do I get in-touch with the national tax agency (i.e. Skatteverket)?
Yes, individual salary information at Swedish universities fall under "offentlighetsprincipen" (the principle of public access to official records), unless they are explicitly classified, which would be very rare. (See for example this document from Stockholm university describing how "offentlighetsprincipen" applies to university matters.)

The easiest way to obtain them is probably to contact the HR department (personalavdelning) at the university/faculty in question.