valuation techniques 2013 cash equivalents are mostly comprised of short-term money-market instruments and are valued at cost , which approximates fair value . u.s . equity securities and international equity securities categorized as level 1 are traded on active national and international exchanges and are valued at their closing prices on the last trading day of the year . for u.s . equity securities and international equity securities not traded on an active exchange , or if the closing price is not available , the trustee obtains indicative quotes from a pricing vendor , broker or investment manager . these securities are categorized as level 2 if the custodian obtains corroborated quotes from a pricing vendor or categorized as level 3 if the custodian obtains uncorroborated quotes from a broker or investment manager . commingled equity funds categorized as level 1 are traded on active national and international exchanges and are valued at their closing prices on the last trading day of the year . for commingled equity funds not traded on an active exchange , or if the closing price is not available , the trustee obtains indicative quotes from a pricing vendor , broker or investment manager . these securities are categorized as level 2 if the custodian obtains corroborated quotes from a pricing vendor . fixed income investments categorized as level 2 are valued by the trustee using pricing models that use verifiable observable market data ( e.g. , interest rates and yield curves observable at commonly quoted intervals and credit spreads ) , bids provided by brokers or dealers or quoted prices of securities with similar characteristics . fixed income investments are categorized as level 3 when valuations using observable inputs are unavailable . the trustee typically obtains pricing based on indicative quotes or bid evaluations from vendors , brokers or the investment manager . in addition , certain other fixed income investments categorized as level 3 are valued using a discounted cash flow approach . significant inputs include projected annuity payments and the discount rate applied to those payments . certain commingled equity funds , consisting of equity mutual funds , are valued using the nav . the nav valuations are based on the underlying investments and typically redeemable within 90 days . private equity funds consist of partnership and co-investment funds . the nav is based on valuation models of the underlying securities , which includes unobservable inputs that cannot be corroborated using verifiable observable market data . these funds typically have redemption periods between eight and 12 years . real estate funds consist of partnerships , most of which are closed-end funds , for which the nav is based on valuation models and periodic appraisals . these funds typically have redemption periods between eight and 10 years . hedge funds consist of direct hedge funds for which the nav is generally based on the valuation of the underlying investments . redemptions in hedge funds are based on the specific terms of each fund , and generally range from a minimum of one month to several months . contributions and expected benefit payments the funding of our qualified defined benefit pension plans is determined in accordance with erisa , as amended by the ppa , and in a manner consistent with cas and internal revenue code rules . we made contributions of $ 5.0 billion to our qualified defined benefit pension plans in 2018 , including required and discretionary contributions . as a result of these contributions , we do not expect to make contributions to our qualified defined benefit pension plans in 2019 . the following table presents estimated future benefit payments , which reflect expected future employee service , as of december 31 , 2018 ( in millions ) : .
what was the percentage of the change in the employee matching contributions from 2017 to 2018
defined contribution plans we maintain a number of defined contribution plans , most with 401 ( k ) features , that cover substantially all of our employees . under the provisions of our 401 ( k ) plans , we match most employees 2019 eligible contributions at rates specified in the plan documents . our contributions were $ 658 million in 2018 , $ 613 million in 2017 and $ 617 million in 2016 , the majority of which were funded using our common stock . our defined contribution plans held approximately 33.3 million and 35.5 million shares of our common stock as of december 31 , 2018 and 2017. .