The public library probably have the local "Tax-calendar" (taxeringskalendern). Like an old fashioned phone book except instead of phone numbers it has the taxed income for everyone in your town for the last year (there is of course web sites with this info too but no free service that I know of). Spent an hour at the library looking up my coworkers salaries when prepping for my first pay negotiation many years ago.
I wonder if the publicity works well against work via tax evasion. Anyone can combine whatever you do with your ID. If you earn a lot of money black on the side (e.g. via drugs dealing), while your income is public and you got this expensive car, then its not just suspicious. Anyone can look you up, figure out you're a sham, and report you.
True, people with low income and flashy spending habits regularly attracts the attention of the tax authorities. So a little bit more savvy criminals funnels their black money through a legit company, in effect paying taxes on a little bit of it. Restaurants was/is popular for this (mostly cash). Used car businesses too.
