Incidentally, Norway appears among the countries with the lowest perception of corruption in the world: #4 among 180 countries (0). It would be interesting to look if there is any correlation with other countries where income records are publicly available.
Salaries are not the entire income. Corruption is usually some income in addition to a salary, but it may still be reflected in the tax record (that is, it's usually some service, board position, etc, not a suitcase full if cash).
Thus public tax records give a better transparency picture than salary records.
0: https://tradingeconomics.com/country-list/corruption-rank