|Years ended December 31,||2015||2014||2013|
|GAAP research and development expenses||$4,070|
|Adjustments to research and development expenses:|
|Certain charges pursuant to our restructuring initiative||(64)|
|Total adjustments to research and development expenses||(153)|
|Adjusted research and development expenses||$3,917|
|GAAP operating income||$8,470||$6,191||$5,867|
|Adjustments to operating income:|
|Certain charges pursuant to our restructuring and other cost-savings initiatives(b)||114||596||71|
|Expense/(benefit) related to various legal proceedings||91||(3)||14|
|Expense resulting from clarified guidance on branded prescription drug fee(c)||–||129||–|
|Stock option expense||–||16||34|
|Total adjustments to operating income||1,582||2,284||1,105|
|Adjusted operating income||$10,052||$8,475||$6,972|
|GAAP operating margin||40.4%||32.0%||32.3%|
|Impact of total adjustments to operating income||7.6%||11.9%||6.0%|
|Adjusted operating margin||48.0%||43.9%||38.3%|
|GAAP net income||$6,939||$5,158|
|Adjustments to operating income||1,582||2,284|
|Income tax effect of the above adjustments(d)||(496)||(717)|
|Other income tax adjustments(e)||(71)||(25)|
|Adjusted net income||$7,954||$6,700|
|Weighted-average shares for diluted EPS||766||770|
|GAAP diluted EPS||$9.06||$6.70|
|Adjusted diluted EPS||$10.38||$8.70|
(a) The adjustments related primarily to non-cash amortization of intangible assets, including developed product technology rights, acquired in business combinations.
(b) The adjustments related primarily to severance, as well as accelerated depreciation and other charges related to the closure of our facilities. 2015 also included gains recognized on the sale of assets related to our site closures.
(c) The adjustments related to the recognition of an additional year of the non-tax deductible branded prescription drug fee, as required by final regulations issued by the Internal Revenue Service.
(d) The tax effect of the adjustments between our GAAP and Adjusted results takes into account the tax treatment and related tax rate(s) that apply to each adjustment in the applicable tax jurisdiction(s). Generally, this results in a tax impact at the U.S. marginal tax rate for certain adjustments, including the majority of amortization of intangible assets, whereas the tax impact of other adjustments, including restructuring expense, depends on whether the amounts are deductible in the respective tax jurisdictions and the applicable tax rate(s) in those jurisdictions.
(e) The adjustments related primarily to certain prior period items excluded from adjusted earnings.