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 at level 3 when valuations using observable inputs are unavailable . the trustee obtains pricing based on indicative quotes or bid evaluations from vendors , brokers or the investment manager . commodities are traded on an active commodity exchange and are valued at their closing prices on the last trading day of the certain commingled equity funds , consisting of equity mutual funds , are valued using the nav.aa thenavaa valuations are based on the underlying investments and typically redeemable within 90 days . private equity funds consist of partnership and co-investment funds . the navaa 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 navaa is based on valuationmodels and periodic appraisals . these funds typically have redemption periods between eight and 10 years . hedge funds consist of direct hedge funds forwhich thenavaa 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 . there were no material contributions to our qualified defined benefit pension plans during 2017 . we will make 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 any material qualified defined benefit cash funding will be required until 2021.we plan to fund these contributions using a mix of cash on hand and commercial paper . while we do not anticipate a need to do so , our capital structure and resources would allow us to issue new debt if circumstances change . the following table presents estimated future benefit payments , which reflect expected future employee service , as of december 31 , 2017 ( in millions ) : .

2018: qualified defined benefit pension plans: 2450
retiree medical and life insurance plans: 180
2019: qualified defined benefit pension plans: 2480
retiree medical and life insurance plans: 180
2020: qualified defined benefit pension plans: 2560
retiree medical and life insurance plans: 180
2021: qualified defined benefit pension plans: 2630
retiree medical and life insurance plans: 180
2022: qualified defined benefit pension plans: 2700
retiree medical and life insurance plans: 180
2023 2013 2027: qualified defined benefit pension plans: 14200
retiree medical and life insurance plans: 820

defined contribution plans wemaintain 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 , wematchmost employees 2019 eligible contributions at rates specified in the plan documents . our contributions were $ 613 million in 2017 , $ 617 million in 2016 and $ 393 million in 2015 , the majority of which were funded using our common stock . our defined contribution plans held approximately 35.5 million and 36.9 million shares of our common stock as of december 31 , 2017 and 2016. .

Questions:
from 2018 to 2019, what was the change in the total of qualified defined benefit pension plans expected payments?
and for the two year period ended two years earlier, what was the variation in the employee total matching contributions?
what is this variation as a percentage of those contributions in 2015?

Answers:
30
224
57%