From an empirical standpoint, is it not more probable that this higher tax rate associated with creating new tax brackets is thwarted by changes in behaviour? For example, people can use tax shelters more wisely. People who earn such income can obviously get help from tax specialists. It would be easier than transferring all of it to another jurisdiction.
Also, has this change in behaviour led to lower incomes than those expected by the Liberal Party, the current government, when it did its fiscal framework.