amortization of intangible assets, partially offset by the settlement of certain unclaimed property and indemnification claims in Q3 2013. 

Income from Operations 

For the reasons discussed above, income from operations increased 10% in 2013, decreased 22% in 2012, and decreased 39% in 2011. 

Interest Income and Expense 

Our interest income was $38 million, $40 million, and $61 million during 2013, 2012, and 2011 . We generally invest our excess cash in investment grade short- to intermediate-term fixed income securities and AAA-rated money market funds. Our interest income corresponds with the average balance of invested funds and the prevailing rates we are earning on them, which vary depending on the geographies and currencies in which they are invested. 

The primary components of our interest expense are related to our long-term debt and capital and financing lease arrangements. Interest expense was $141 million , $92 million , and $65 million in 2013 , 2012 , and 2011 . 

Our long-term debt was $3.2 billion and $3.1 billion as of December 31, 2013 and 2012 . Our other long-term liabilities were $4.2 billion and $2.3 billion as of December 31, 2013 and 2012 . See Item 8 of Part II, “Financial Statements and Supplementary Data—Note 6—Long-Term Debt and Note 7—Other Long-Term Liabilities” for additional information. 

Other Income (Expense)

Other income (expense), net was $(136) million, $(80) million, and $76 million during 2013 , 2012 , and 2011 . The primary component of other income (expense), net is related to foreign-currency gains (losses) on intercompany balances. 

Income Taxes 

Our effective tax rate is subject to significant variation due to several factors, including variability in our pre-tax and taxable income and loss and the mix of jurisdictions to which they relate, changes in how we do business, acquisitions (including integrations) and investments, audit developments, foreign currency gains (losses), changes in law, regulations, and administrative practices, and relative changes of expenses or losses for which tax benefits are not recognized. 

We recorded a provision for income taxes of $161 million, $428 million, and $291 million in 2013 , 2012 , and 2011 . Our effective tax rate in 2013 was lower than the 35% U.S. federal statutory rate and our effective tax rate in 2012 primarily due to the favorable impact of earnings in lower tax rate jurisdictions, a decline in the proportion of our losses for which we may not realize a related tax benefit, and the retroactive extension of the U.S. federal research and development credit, which expired in December 2013. The favorable impact of earnings in lower tax rate jurisdictions primarily relates to our European operations, which are headquartered in Luxembourg. Losses for which we may not realize a related tax benefit, primarily due to losses of foreign subsidiaries, reduce our pre-tax income without a corresponding reduction in our tax expense, and therefore increase our effective tax rate. In 2013, we recognized tax benefits for a greater proportion of these losses as compared to 2012. We have recorded valuation allowances against the deferred tax assets associated