Norway's online tax-return disclosure (2001) — a natural experiment that narrowed within-firm gender wage gaps by 8.7%

In 2001 Norway made individual tax returns, long available as printed lists, searchable online. A February 2026 Statistics Norway discussion paper (Carvalho and Vattø) uses matched employer-employee data and a difference-in-differences design to test whether this general transparency affected gender wage gaps.
It finds that within-firm gender wage gaps fell by 2.2 percentage points (8.7 percent), driven by rising female wages. Effects were strongest in private-sector firms, in industries with initially larger gaps, and in municipalities that previously lacked easy access to printed tax lists.
Wage gains were concentrated among job-changing women, which suggests that broad transparency works mainly by improving information for job search and bargaining rather than through employer reporting duties.
Caveats: the reform was not designed as a gender-equality measure, the evidence comes from one country, and open tax data involves privacy trade-offs that many jurisdictions would not accept.

Read the full analysis: https://www.ssb.no/en/arbeid-og-lonn/lonn-og-arbeidskraftkostnader/artikler/does-tax-transparency-influence-wage-setting