Benefit Plans and Note 11. Pension and Postretirement Benefit Plans and Defined Contribution Plans). Beginning on January 1, 2011, for employees hired in the U.S. and Puerto Rico after December 31, 2010, we no longer offer a defined benefit plan and, instead, offer an enhanced benefit under our defined contribution plan. In addition to the standard matching contribution by the Company, the enhanced benefit provides an automatic Company contribution for such eligible employees based on age and years of service. Also, on May 8, 2012, we announced to employees that as of January 1, 2018, Pfizer will transition its U.S. and Puerto Rico employees from its defined benefit plans to an enhanced defined contribution savings plan.

The accounting for benefit plans is highly dependent on actuarial estimates, assumptions and calculations, which result from a complex series of judgments about future events and uncertainties. The assumptions and actuarial estimates required to estimate the employee benefit obligations for the defined benefit and postretirement plans may include the discount rate; expected salary increases; certain employee-related factors, such as turnover, retirement age and mortality (life expectancy); expected return on assets; and healthcare cost trend rates.

Our assumptions reflect our historical experiences and our best judgment regarding future expectations that have been deemed reasonable by management. The judgments made in determining the costs of our benefit plans can materially impact our results of operations.

   The following table provides the expected versus actual rate of return on plan assets and the discount rate used to determine the benefit obligations for the U.S. qualified pension plans:

      The assumption for the expected rate of return on assets for our U.S. and international plans reflects our actual historical return experience and our long-term assessment of forward-looking return expectations by asset classes, which is used to develop a weighted-average expected return based on the implementation of our targeted asset allocation in our respective plans (see Notes to Consolidated Financial Statements— Note 11D. Pension and Postretirement Benefit Plans and Defined Contribution Plans: Plan Assets for asset allocation ranges and actual asset allocations for 2012 and 2011). The expected return for our U.S. plans and the majority of our international plans is applied to the fair market value of plan assets at each year end. Holding all other assumptions constant, the effect of a 0.5 percentage-point decline in the return-on- assets assumption would increase our 2013 U.S. qualified pension plans’ pre-tax expense by approximately $60 million.

The discount rate used in calculating our U.S. defined benefit plan obligations as of December 31, 2012 is 4.3%, which represents a 0.8 percentage-point decrease from our December 31, 2011 rate of 5.1%. The discount rate for our U.S. defined benefit plans is determined annually and evaluated and modified to reflect at year-end the prevailing market rate of a portfolio of high-quality corporate bond investments rated AA or better that would provide the future cash flows