The Company reported full year 2012 U.S. GAAP net income of $1.1 billion and earnings of $3.33 per diluted share, compared to $1.1 billion or $2.72 per diluted share in the prior year. Full year 2012 Adjusted Net Income totaled $1,240 million, or $3.84 per diluted share, which includes the favorable impact of share repurchases in 2012 and the unfavorable impact from the variable 2010 Long-Term Incentive Plan, compared to Adjusted Net Income of $1,169 million, or $2.78 per diluted share, in the prior year period.
Full year 2012 Adjusted EBITDA totaled $2,142 million, compared to $2,150 million in the prior year period. Adjusted EBITDA margin for the full year 2012 improved 40 basis points to 13.8%, from 13.4% in the prior year period. Adjusted EBITDA in 2012 reflects strong performance in the Electrical/Electronic Architecture, Powertrain and Electronics and Safety segments, partially offset by lower earnings in our Thermal business segment, the unfavorable impacts of currency exchange, and $64 million of increased expense resulting from the variable accounting impacts related to the Company's 2010 Long-Term Incentive Plan. Excluding the variable impacts of the 2010 Long-Term Incentive Plan, Adjusted EBITDA margin for the full year 2012 was 14.2%.
Interest expense for 2012 totaled $136 million, compared to $123 million in the prior year period, primarily reflecting the debt financing incurred at the end of the first quarter of 2011 to redeem the ownership interests previously held by General Motors Company and the Pension Benefit Guaranty Corporation.
Tax expense for 2012 was $212 million, resulting in an effective tax rate of approximately 16%, compared to $305 million, or an effective rate of 20%, in the prior year period. The improvement in 2012 primarily reflects the impacts of the geographic mix of pretax earnings, tax planning initiatives, and the recognition of discrete tax items.