A 2012 investigation by the U.S. Senate Permanent Subcommittee on Investigations, led by Senator Carl Levin, found that Microsoft had used subsidiaries in Puerto Rico, Ireland, Singapore and Bermuda to shift profits offshore and avoid more than $6.5 billion in U.S. taxes over three years. The report detailed how Microsoft routed nearly half of its U.S. revenue through a Puerto Rican affiliate to cut its tax bill. Levin stressed that Microsoft had broken no laws and was exploiting loopholes Congress created, and Microsoft said it complied fully with U.S. tax rules. The findings put Microsoft — the company Bill Gates founded and then chaired — at the center of the debate over corporate tax avoidance.