related to actuarial assumptions used to determine our pension expense and related obligation. We believe the most critical assumptions are related to (1) the discount rate used to determine the present value of the liabilities and (2) the expected long-term rate of return on plan assets. All of our actuarial assumptions are reviewed annually. Changes in these assumptions could have a material impact on the measurement of our pension expense and related obligation. 

At each measurement date, we determine the discount rate by reference to rates of high-quality, long-term corporate bonds that mature in a pattern similar to the future payments we anticipate making under the plans. As of December 31, 2011 and 2010, the weighted-average discount rate used to compute our benefit obligation was 4.75 percent and

5.5 percent, respectively. 

The expected long-term rate of return on plan assets is based upon the long-term outlook of our investment strategy as well as our historical returns and volatilities for each asset class. We also review current levels of interest rates and inflation to assess the reasonableness of our long-term rates. Our pension plan investment objective is to ensure all of our plans have sufficient funds to meet their benefit obligations when they become due. As a result, the Company periodically revises asset allocations, where appropriate, to improve returns and manage risk. The weighted-average expected long-term rate of return used to calculate our net periodic benefit cost was 8.25 percent and 8.0 percent in 2011 and 2010, respectively. 

In 2011, the Company's total pension expense related to defined benefit plans was $249 million. In 2012, we expect our total pension expense to be approximately $200 million. The anticipated decrease is primarily due to approximately $953 million of contributions the Company expects to make to various plans in 2012, of which $900 million was contributed to the Company's U.S. pension plans during the first quarter of 2012. The expected favorable impact of this item will be partially offset by the expected unfavorable impact of a decrease in the weighted-average discount rate used to calculate the Company's benefit obligation. The estimated impact of an additional 50-basis-point decrease in the discount rate on our 2012 pension expense is an increase to our pension expense of approximately $39 million. Additionally, the estimated impact of a 50-basis-point decrease in the expected long-term rate of return on plan assets on our 2012 pension expense is an increase to our pension expense of approximately $25 million. 

The sensitivity information provided above is based only on changes to the actuarial assumptions used for our U.S. pension plans. As ofDecember 31, 2011, the Company's primary U.S. plans represented 58 percent and 60 percent of the Company's consolidated projected pension benefit obligation and pension assets, respectively. Refer to Note 13 of Notes to Consolidated Financial Statements for additional information about our pension plans and related actuarial assumptions. 

Revenue Recognition 

We recognize revenue when persuasive evidence of an arrangement exists, delivery of