That’s perhaps the boldest declaration in the joint statement from G-20 world leaders meeting today in London.

The communiqué, which pledges $1.1 trillion in global stimulus spending and tighter supervision and regulation of the global economy, did not commit the leaders to another round of stimulus spending as President Obama wanted, nor cross-border financial regulation as Germany and France hoped.

But it does announce a new tool of transparency: the formal blacklisting of tax haven countries that have not agreed to international information sharing agreements. Fast money operations like  AIG haved use these countries to claim they don’t have to pay  U.S. taxes. Estimates of lost tax revenue range from $40 billion to $123 billion annually, according to recent Treasury Department study cited by The Wall Street Journal. The communique strengthens Obama’s efforts get capture these revenues to pay for his ambitious domestic agenda.