Years ended December 31, | 2013 | 2012 | 2011 | |||||
U.S. federal statutory tax | 35.0 | % | 35.0 | % | 35.0 | % | ||
Research and development credits | (4.9 | ) | 0.8 | (2.7 | ) | |||
Proposed amendments to the R&E regulations | (3.4 | ) | ||||||
Tax on international activities | (0.1 | ) | (1.2 | ) | (0.6 | ) | ||
Tax deductible dividends | (0.6 | ) | (0.7 | ) | (0.8 | ) | ||
State income tax provision, net of effect on U.S. federal tax | 0.4 | 0.8 | 0.7 | |||||
Federal audit settlement | (7.4 | ) | ||||||
Other provision adjustments | (0.7 | ) | 1.4 | |||||
Effective income tax rate | 26.4 | % | 34.0 | % | 25.6 | % |