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
2019
2020
2021
2022
2023 – 2027
Qualified defined benefit pension plans
$2,450
$2,480
$2,560
$2,630
$2,700
$14,200
Retiree medical and life insurance plans
180
180
180
180
180
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. .

Question: Analyse this data from a financial earnings document. what was the percentage change in the employee total matching contributions from 2015 to 2016
Choices:
617.56997
6.30986
1.75446
0.00057
0.56997
Correct choice index: 4