is applied to the fair value of plan assets at each year-end and the resulting amount is reflected in our net periodic benefit costs in the following year. Holding all other assumptions constant, the effect of a 50 basis point decline in our assumption for the expected annual rate of return on plan assets would increase our 2014 net periodic benefit costs by approximately $101 million, pre-tax.

The actual return on plan assets resulted in an increase in our aggregate plan assets of approximately $2.4 billion during 2013. Discount Rate Used to Measure Plan Obligations

The discount rate used to measure the plan obligations for our U.S. defined benefit plans is determined at least annually and evaluated and modified, as required, to reflect the prevailing market rate of a portfolio of high-quality corporate bond investments, rated AA/Aa or better, that would provide the future cash inflows needed to settle our benefit obligations as they come due. The discount rate used to measure the plan obligations for our international plans is determined at least annually by reference to investment grade corporate bonds, rated AA/Aa or better, including, when there are sufficient data, a yield-curve approach. These discount rate determinations are made in consideration of local requirements.

The measurement of the plan obligations at the end of the year will affect the amount of service cost, interest cost and amortization expense reflected in our net periodic benefit costs in the following year. Holding all other assumptions constant, the effect of a 10 basis point decrease in the discount rate assumptions would increase our 2014 net periodic benefit costs by approximately $30 million, pre-tax, and increase our benefit obligations as of December 31, 2013 by approximately $421 million.

The change in the discount rates used in measuring our plan obligations as of December 31, 2013 resulted in a decrease in the measurement of our aggregate plan obligations by approximately $2.2 billion.

Contingencies

For a discussion about income tax contingencies, see Notes to Consolidated Financial Statements—Note 5D. Tax Matters: Tax Contingencies. For a discussion about legal and environmental contingencies, guarantees and indemnifications, see Notes to Consolidated Financial

ANALYSIS OF THE CONSOLIDATED STATEMENTS OF INCOME

Revenues-Overview

 Total revenues were $51.6 billion in 2013, a decrease of 6% compared to 2012, which reflects an operational decline of $1.9 billion, or 4%. The operational decrease was primarily the result of:

• the continued erosion of branded Lipitor in the U.S., developed Europe and certain other developed markets (approximately $1.7 billion);

• the loss of exclusivity for Geodon in March 2012 in the U.S. (approximately $130 million);

• other product losses of exclusivity (approximately $1.3 billion);

• the ongoing expiration of the Spiriva collaboration in certain countries (approximately $475 million);

• decreased government purchases of the Prevnar family of products and Enbrel in certain emerging markets (approximately $160 million); and

• lower revenues from generic atorvastatin (approximately $145 million),

partially