R. RETIREMENT PLANS Defined Contribution Plans Defined Benefit Plans unrecognized compensation cost related to restricted stock and RSUs, which is expected to be recognized over a weighted average period of 1.6 years. A summary of restricted stock and RSU activity during 2020 follows: The total fair value of vesting shares was $103 in 2020, $88 in 2019 and $242 in 2018. We provide retirement benefits to eligible employees through a variety of plans: We provide eligible employees the opportunity to participate in defined contribution plans (commonly known as 401(k) plans), which permit contributions on a before-tax and after-tax basis. Employees may contribute to various investment alternatives. In most of these plans, we match a portion of the employees’ contributions. Our contributions to these plans totaled $379 in 2020, $333 in 2019 and $302 in 2018. The defined-contribution plans held approximately 19 million shares of our common stock, representing approximately 7% of our outstanding shares on December 31, 2020 and 2019. Plan Descriptions.  We have trusteed, qualified pension plans covering eligible employees aligned with the markets in our business: U.S. government, non-U.S. government and commercial. Some of these plans require employees to make contributions to the plan. We also sponsor several non-qualified pension plans, which provide eligible executives with additional benefits, including excess benefits over limits imposed on qualified plans by federal tax law. The principal factors affecting the benefits earned by participants in our pension plans are employees’ years of service and compensation levels. Our primary U.S. pension plans, which comprise the majority of our unfunded obligation, were closed to new salaried participants on January 1, 2007, and were closed to new hourly participants in subsequent collective bargaining agreements over the next several years. Additionally, we have made several changes to these plans for certain participants that limit or cease the benefits that accrue for future service. In addition to pension benefits, we maintain plans that provide post-retirement healthcare and life insurance coverage for certain employees and retirees. These benefits vary by employment status, age, 86 Substantially all of our plans use a December 31 measurement date consistent with our fiscal year. • Defined contribution • Defined benefit ◦ Pension (qualified and non-qualified) ◦ Other post-retirement benefit In Shares and Dollars Shares/ Share-Equivalent  Units Weighted Average Grant-Date Fair Value Per Share Nonvested at December 31, 2019 1,224,364  $ 181.11  Granted 559,168  170.57  Vested (609,870) 172.23  Forfeited (23,511) 173.91  Nonvested at December 31, 2020 1,150,151  $ 180.98 