General and Administrative Expenses In accordance with industry practice and the regulations that govern the cost accounting requirements for government contracts, most general and administrative expenses are considered allowable and allocable costs on government contracts.
These costs are allocated to contracts in progress on a systematic basis, and contract performance factors include this cost component as an element of cost.2017 - General and administrative expenses in 2017 decreased $53 million, or 9%, compared to 2016.
This decrease was primarily driven by favorable changes in the FAS/CAS Adjustment.2016 - General and administrative expenses in 2016 decreased $46 million, or 7%, compared to 2015.
This decrease was primarily driven by favorable changes in the FAS/CAS Adjustment and lower current state tax expense.
Impairment of Goodwill As discussed above under Critical Accounting Policies, Estimates and Judgments, we perform impairment tests for goodwill as of November 30 each year, or when evidence of potential impairment exists.
We record a charge to operations when we determine that an impairment has occurred.
We recorded goodwill impairment charges in 2015 of $75 million in our Technical Solutions segment.
See Note 12: Goodwill and Other Purchased Intangible Assets in Item 8.
Operating Income We consider operating income to be an important measure for evaluating our operating performance, and, as is typical in the industry, we define operating income as revenues less the related cost of producing the revenues and general and administrative expenses.
We internally manage our operations by reference to "segment operating income," which is defined as operating income before the FAS/CAS Adjustment and non-current state income taxes, neither of which affects segment performance.
Segment operating income is not a recognized measure under GAAP.
When analyzing our operating performance, investors should use segment operating income in addition to, and not as an alternative for, operating income or any other performance measure presented in accordance with GAAP.
It is a measure we use to evaluate our core operating performance.
We believe segment operating income reflects an additional way of viewing aspects of our operations that, when viewed with our GAAP results, provides a more complete understanding of factors and trends affecting our business.
We believe the measure is used by investors and is a useful indicator to measure our performance.
Because not all companies use identical calculations, our presentation of segment operating income may not be comparable to similarly titled measures of other companies.
The following table reconciles segment operating income to operating income:
## Table 0 ##
Segment Operating Income 2017 - Segment operating income in 2017 was $688 million, compared to $715 million in 2016.
The decrease was primarily due to lower risk retirement on the delivered USS John P.  Murtha (LPD 26), lower volume and risk retirement in the Virginia class (SSN 774) submarine program and Arleigh Burke class (DDG 51) destroyers, favorable changes in overhead costs in 2016, the receipt in 2016 of a local government incentive grant, and the establishment of an allowance for accounts receivable on a nuclear and environmental commercial contract in 2017, partially offset by higher risk retirement on Tripoli (LHA 7) and Portland (LPD 27), the resolution of
The funded status of these plans as of December 31, 2018 and 2017, was as follows:
## Table 1 ##
(1) Included in miscellaneous other assets.
(2) Included in other current liabilities and current portion of postretirement plan liabilities, respectively.
(3) Included in pension plan liabilities and other postretirement plan liabilities, respectively.
The Projected Benefit Obligation ("PBO"), Accumulated Benefit Obligation ("ABO"), and asset values for the Company's qualified pension plans were $6,336 million, $6,017 million, and $5,726 million, respectively, as of December 31, 2018, and $6,596 million, $6,202 million, and $5,837 million, respectively, as of December 31, 2017.
The PBO represents the present value of pension benefits earned through the end of the year, with allowance for future salary increases.
The ABO is similar to the PBO, but does not provide for future salary increases.
The PBO and fair value of plan assets for all qualified and non-qualified pension plans with PBOs in excess of plan assets were $6,519 million and $5,726 million, respectively, as of December 31, 2018, and $5,386 million and $4,440 million, respectively, as of December 31, 2017.
The ABO and fair value of plan assets for all qualified and non-qualified pension plans with ABOs in excess of plan assets were $6,183 million and $5,726 million, respectively, as of December 31, 2018, and $5,001 million and $4,440 million, respectively, as of December 31, 2017.
The ABO for all pension plans was $6,183 million and $6,367 million as of December 31, 2018 and 2017, respectively
Equity Compensation Plan Information The following table presents the equity securities available for issuance under our equity compensation plans as of December 31, 2018.
## Table 2 ##
(1) Includes grants made under the Huntington Ingalls Industries, Inc.  2012 Long-Term Incentive Stock Plan (the "2012 Plan"), which was approved by our stockholders on May 2, 2012, and the Huntington Ingalls Industries, Inc.  2011 Long-Term Incentive Stock Plan (the "2011 Plan"), which was approved by the sole stockholder of HII prior to its spin-off from Northrop Grumman Corporation.
Of these shares, 27,123 were stock rights granted under the 2011 Plan.
In addition, this number includes 31,697 stock rights, 5,051 restricted stock rights, and 335,293 restricted performance stock rights granted under the 2012 Plan, assuming target performance achievement.
(2) There are no awards made under plans not approved by security holders.
ITEM 13.
CERTAIN RELATIONSHIPS AND RELATED TRANSACTIONS, AND DIRECTOR INDEPENDENCE Information as to certain relationships and related transactions and director independence will be incorporated herein by reference to the Proxy Statement for our 2019 Annual Meeting of Stockholders, to be filed within 120 days after the end of the Company’s fiscal year.
ITEM 14.
PRINCIPAL ACCOUNTANT FEES AND SERVICES Information as to principal accountant fees and services will be incorporated herein by reference to the Proxy Statement for our 2019 Annual Meeting of Stockholders, to be filed within 120 days after the end of the Company’s fiscal year.

<table><tr><td></td><td colspan="3">Year Ended December 31</td><td colspan="2">2017 over 2016</td><td colspan="2">2016 over 2015</td></tr><tr><td>($ in millions)</td><td>2017</td><td>2016</td><td>2015</td><td>Dollars</td><td>Percent</td><td>Dollars</td><td>Percent</td></tr><tr><td>Segment operating income (loss)</td><td>$688</td><td>$715</td><td>$667</td><td>$-27</td><td>-4%</td><td>$48</td><td>7%</td></tr><tr><td>FAS/CAS Adjustment</td><td>189</td><td>145</td><td>104</td><td>44</td><td>30%</td><td>41</td><td>39%</td></tr><tr><td>Non-current state income taxes</td><td>-12</td><td>-2</td><td>-2</td><td>-10</td><td>-500%</td><td>—</td><td>—%</td></tr><tr><td>Operating income (loss)</td><td>$865</td><td>$858</td><td>$769</td><td>$7</td><td>1%</td><td>$89</td><td>12%</td></tr></table>
<table><tr><td></td><td colspan="2">Pension Benefits December 31</td><td colspan="2">Other Benefits December 31</td></tr><tr><td>($ in millions)</td><td>2018</td><td>2017</td><td>2018</td><td>2017</td></tr><tr><td>Change in Benefit Obligation</td><td></td><td></td><td></td><td></td></tr><tr><td>Benefit obligation at beginning of year</td><td>$6,778</td><td>$6,050</td><td>$553</td><td>$578</td></tr><tr><td>Service cost</td><td>157</td><td>146</td><td>8</td><td>10</td></tr><tr><td>Interest cost</td><td>254</td><td>266</td><td>21</td><td>24</td></tr><tr><td>Plan participants' contributions</td><td>6</td><td>4</td><td>8</td><td>8</td></tr><tr><td>Plan amendments</td><td>—</td><td>74</td><td>—</td><td>-10</td></tr><tr><td>Actuarial loss (gain)</td><td>-441</td><td>457</td><td>-73</td><td>-15</td></tr><tr><td>Benefits paid</td><td>-235</td><td>-219</td><td>-38</td><td>-42</td></tr><tr><td>Benefit obligation at end of year</td><td>6,519</td><td>6,778</td><td>479</td><td>553</td></tr><tr><td>Change in Plan Assets</td><td></td><td></td><td></td><td></td></tr><tr><td>Fair value of plan assets at beginning of year</td><td>5,837</td><td>4,911</td><td>—</td><td>—</td></tr><tr><td>Actual return on plan assets</td><td>-398</td><td>840</td><td>—</td><td>—</td></tr><tr><td>Employer contributions</td><td>516</td><td>301</td><td>30</td><td>34</td></tr><tr><td>Plan participants' contributions</td><td>6</td><td>4</td><td>8</td><td>8</td></tr><tr><td>Benefits paid</td><td>-235</td><td>-219</td><td>-38</td><td>-42</td></tr><tr><td>Fair value of plan assets at end of year</td><td>5,726</td><td>5,837</td><td>—</td><td>—</td></tr><tr><td>Funded status</td><td>$-793</td><td>$-941</td><td>$-479</td><td>$-553</td></tr><tr><td>Amounts Recognized in the Consolidated Statements of Financial Position:</td><td></td><td></td><td></td><td></td></tr><tr><td>Pension plan assets<sup>-1</sup></td><td>$—</td><td>$6</td><td>$—</td><td>$—</td></tr><tr><td>Current liability<sup>-2</sup></td><td>-29</td><td>-25</td><td>-131</td><td>-139</td></tr><tr><td>Non-current liability<sup>-3</sup></td><td>-764</td><td>-922</td><td>-348</td><td>-414</td></tr><tr><td>Accumulated other comprehensive loss (income) (pre-tax) related to:</td><td></td><td></td><td></td><td></td></tr><tr><td>Prior service costs (credits)</td><td>99</td><td>122</td><td>-53</td><td>-75</td></tr><tr><td>Net actuarial loss (gain)</td><td>1,780</td><td>1,477</td><td>-88</td><td>-18</td></tr></table>
<table><tr><td>Plan category</td><td>Number of Securities to be Issued Upon Exercise of Outstanding Options, Warrants and Rights<sup>-1</sup> (a)(b)</td><td>Weighted-Average Exercise Price of Outstanding Options,Warrants and Rights</td><td>Number of Securities Remaining Available for Future Issuance Under Equity Compensation Plans (Excluding SecuritiesReflected in Column (a)) (c)</td></tr><tr><td>Equity compensation plans approved by security holders</td><td>399,165</td><td>$0.00</td><td>3,995,600</td></tr><tr><td>Equity compensation plans not approved by security holders<sup>-2</sup></td><td>—</td><td>—</td><td>—</td></tr><tr><td>Total</td><td>399,165</td><td>$0.00</td><td>3,995,600</td></tr></table>

Question: Which year is Benefit obligation at end of year the least, in term of Pension Benefits December 31?
Answer: 2018