How did Merck record an 11% tax rate last year? The Senate finance chairman would like to know

With tax day right around the corner in the U.S., Merck & Co. is the latest Big Pharma to find itself in the crosshairs of a congressional tax probe.

Sen. Ron Wyden, the chairman of the Senate Finance Committee, on Monday wrote to Merck CEO Robert Davis asking how the company managed to pay a tax rate of just 11% last year. As Sen. Wyden notes, Merck's "legal domicile" is in the U.S., and that's where most of the company's R&D activities take place.