foreign exchange rates remained the same as those in effect in the comparable prior year period. 

Guidance 

We provided guidance on January 28, 2016 , in our earnings release furnished on Form 8-K as set forth below. These forward-looking statements reflect Amazon.com’s expectations as of January 28, 2016 , and are subject to substantial uncertainty. Our results are inherently unpredictable and may be materially affected by many factors, such as fluctuations in foreign exchange rates, changes in global economic conditions and customer spending, world events, the rate of growth of the Internet and online commerce, as well as those outlined in Item 1A of Part I, “Risk Factors.” 

First Quarter 2016 Guidance 

Net sales are expected to be between $26.5 billion and $29.0 billion, or to grow between 17% and 28% compared with first quarter 2015. 

Operating income is expected to be between $100 million and $700 million, compared with $255 million in first quarter 2015. 

This guidance includes approximately $600 million for stock-based compensation and other operating expense (income), net. It assumes, among other things, that no additional business acquisitions, investments, restructurings, or legal settlements are concluded and that there are no further revisions to stock-based compensation estimates. 

Quantitative and Qualitative Disclosures About Market Risk 

We are exposed to market risk for the effect of interest rate changes, foreign currency fluctuations, and changes in the market values of our investments. Information relating to quantitative and qualitative disclosures about market risk is set forth below and in Item 7 of Part II, “Management’s Discussion and Analysis of Financial Condition and Results of Operations—Liquidity and Capital Resources.” 

Interest Rate Risk 

Our exposure to market risk for changes in interest rates relates primarily to our investment portfolio and our long-term debt. Our long-term debt is carried at amortized cost and fluctuations in interest rates do not impact our consolidated financial statements. However, the fair value of our debt, which pays interest at a fixed rate, will generally fluctuate with movements of interest rates, increasing in periods of declining rates of interest and declining in periods of increasing rates of interest. All of our cash equivalent and marketable fixed income securities are designated as available-for-sale and, accordingly, are presented at fair value on our consolidated balance sheets. We generally invest our excess cash in investment grade short- to intermediate-term fixed income securities and AAA-rated money market funds. Fixed income securities may have their fair market value adversely affected due to a rise in interest rates, and we may suffer losses in principal if forced to sell securities that have declined in market value due to changes in interest rates. 

The fair value of our debt will fluctuate with movements of interest rates, increasing in periods of declining rates of interest and declining in periods of increasing rates of interest. Based upon quoted market prices and Level 2 inputs, the fair value of our total debt was $8.8 billion as of December