A unilateral global regime is the only complete solution to prevent capital from fleeing to lower-tax locales (e.g. Cayman Islands).

That said, the same incentives for smaller countries to offer lower tax rates will make them unwilling to agree to a global regime. And a global taxation regime would require a degree of international cooperation that has never been seen.

Janet is laying the groundwork for a potential policy which would take decades if not 100 years to come to fruition. She is extremely smart and intentional about her words, as a leader of the Fed.