Leuz,2016 documented that
an international setting that measures regulatory effects in multiple countries at different points in time is also less susceptible to concurrent but unrelated economic shocks because confounding shocks need to be correlated with the implementation dates of the regulations across these countries to induce the results
I am wondering why the "implementation in different time" can help to "less susceptible to concurrent but unrelated economic shocks". I did not fully understand what the author describes. Because it is correct that confounding shocks still the same year as the implementation year in each country.