US Tax Clampdown Shuts Door on Pfizer/Allergan Merger

The world's biggest pharmaceutical merger was called off today by Pfizer and Allergan, a company in Ireland. It's being called a victory for President Obama, who announced yesterday that actions by the Treasury, “directly go[es] at what's called corporate inversions. They are not new. Simply put, in layman's terms, it's when big corporations acquire small corp -- uh companies -- and then change their address to another country on paper in order to get out of paying their fair share of taxes here at home."

We hear more from Matthew Herper, who reports on Science and Medicine for Forbes magazine.