The funded status of the Company's plans as of December 31, 2015 and 2014, was as follows
||Pension Benefits December 31|Other Benefits December 31|
|($ in millions)|2015|2014|2015|2014|
|Change in Benefit Obligation|||||
|Benefit obligation at beginning of year|$5,671|$4,730|$650|$616|
|Service cost|150|136|13|13|
|Interest cost|242|253|27|30|
|Plan participants' contributions|11|26|6|7|
|Actuarial loss (gain)|-254|714|-91|24|
|Benefits paid|-185|-168|-39|-40|
|Curtailments|—|-20|—|—|
|Benefit obligation at end of year|5,635|5,671|566|650|
|Change in Plan Assets|||||
|Fair value of plan assets at beginning of year|4,731|4,310|—|—|
|Actual return on plan assets|-47|437|—|—|
|Employer contributions|103|126|33|33|
|Plan participants' contributions|11|26|6|7|
|Benefits paid|-185|-168|-39|-40|
|Fair value of plan assets at end of year|4,613|4,731|—|—|
|Funded status|$-1,022|$-940|$-566|$-650|
|Amounts Recognized in the Consolidated Statements of Financial Position:|||||
|Pension plan assets|$—|$17|$—|$—|
|Current liability-1|-21|-18|-143|-143|
|Non-current liability-2|-1,001|-939|-423|-507|
|Accumulated other comprehensive loss (income) (pre-tax) related to:|||||
|Prior service costs (credits)|86|105|-105|-125|
|Net actuarial loss (gain)|1,433|1,374|-21|73|

(1) Included in other current liabilities and current portion of postretirement plan liabilities, respectively.
(2) 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 $5,490 million, $5,146 million, and $4,613 million, respectively, as of December 31, 2015, and $5,529 million, $5,124 million, and $4,731 million, respectively, as of December 31, 2014.
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 $5,635 million and $4,613 million, respectively, as of December 31, 2015, and $4,394 million and $3,438 million, respectively, as of December 31, 2014.
The ABO and fair value of plan assets for all qualified and non-qualified pension plans with ABOs in excess of plan assets were $4,051 million and $3,391 million, respectively, as of December 31, 2015, and $3,981 million and $3,438 million, respectively, as of December 31, 2014.
The ABO for all pension plans was $5,273 million and $5,244 million as of December 31, 2015 and 2014, respectively.
The changes in amounts recorded in accumulated other comprehensive income (loss) were as follows:
FAS/CAS Adjustment The FAS/CAS Adjustment represents the difference between our pension and postretirement plan expense under FAS and under CAS.
||Year Ended December 31|2015 over 2014|2014 over 2013|
|($ in millions)|2015|2014|2013|Dollars|Percent|Dollars|Percent|
|FAS expense|$-168|$-155|$-257|$-13|-8%|$102|40%|
|CAS cost|272|227|196|45|20%|31|16%|
|FAS/CAS Adjustment|$104|$72|$-61|$32|44%|$133|218%|

2015 - The FAS/CAS Adjustment in 2015 was a net benefit of $104 million, compared to a net benefit of $72 million in 2014.
The favorable change was driven by the phase-in of Harmonization and better than expected 2014 asset returns, partially offset by higher FAS expense primarily due to lower discount rates at the end of 2014.2014 - The FAS/CAS Adjustment in 2014 was a net benefit of $72 million, compared to a net expense of $61 million in 2013.
The favorable change was driven by lower FAS expense, due primarily to higher discount rates and plan assets at the end of 2013, the full year effect of the 2013 postretirement benefits amendment, and the phase-in of Harmonization.
We expect the FAS/CAS Adjustment in 2016 to be a net benefit of approximately $137 million ($161 million FAS and $298 million CAS), primarily driven by the continued phase-in of Harmonization and higher FAS discount rates, partially offset by lower than expected 2015 asset returns.
The expected FAS/CAS Adjustment is subject to change during 2016, when we remeasure our actuarial estimate of the unfunded benefit obligation for CAS with updated census data and other items.
Deferred State Income Taxes Deferred state income taxes reflect the change in deferred state tax assets and liabilities in the relevant period.
These amounts are recorded within operating income, while the current period state income tax expense is charged to contract costs and included in cost of sales and service revenues in segment operating income.2015 - The deferred state income tax expense remained constant at $2 million in 2015 and 2014.
Deferred state tax expense in 2015 was primarily attributable to changes in the timing of contract taxable income and pension related adjustments, partially offset by a reduction in the valuation allowance for state tax credit carryforwards.2014 - The deferred state income tax expense in 2014 was $2 million, compared to a benefit of $6 million in 2013.
This change was primarily attributable to non-recurring adjustments related to establishing a valuation allowance for a state tax loss carryforward and the true-up of 2013 deferred taxes.
These increases were partially offset by changes in the timing of contract taxable income and reserves that are not currently deductible for tax purposes.
Interest Expense 2015 - Interest expense in 2015 was $137 million, compared to $149 million in 2014.
The decrease was primarily a result of refinancing 6.875% senior notes with 5.000% senior notes and repayment in full of the term loans, partially offset by loss on early extinguishment of debt.
See Note 14: Debt in Item 8.2014 - Interest expense in 2014 was $149 million, compared to $118 million in 2013.
The increase was primarily a result of a loss on the early extinguishment of debt in the fourth quarter of 2014.
See Note 14: Debt in Item 8.
Federal Income Taxes 2015 - Our effective tax rate on earnings from continuing operations was 36.1% in 2015, compared to 33.3% in 2014.
The increase in our effective tax rate for 2015 was primarily attributable to adjustments to the domestic manufacturing deduction and an increase in the goodwill impairment that is not amortizable for tax purposes.
Advance Payments and Billings in Excess of Revenues - Payments received in excess of inventoried costs and revenues are recorded as advance payment liabilities.
Property, Plant, and Equipment - Depreciable properties owned by the Company are recorded at cost and depreciated over the estimated useful lives of individual assets.
Major improvements are capitalized while expenditures for maintenance, repairs, and minor improvements are expensed.
Costs incurred for computer software developed or obtained for internal use are capitalized and amortized over the expected useful life of the software, not to exceed nine years.
Leasehold improvements are amortized over the shorter of their useful lives or the term of the lease.
The remaining assets are depreciated using the straight-line method, with the following lives:
||Years|
|Land improvements|3|-|40|
|Buildings and improvements|3|-|60|
|Capitalized software costs|3|-|9|
|Machinery and other equipment|2|-|45|

The Company evaluates the recoverability of its property, plant, and equipment when there are changes in economic circumstances or business objectives that indicate the carrying value may not be recoverable.
The Company's evaluations include estimated future cash flows, profitability, and other factors affecting fair value.
As these assumptions and estimates may change over time, it may or may not be necessary to record impairment charges.
Leases - The Company uses its incremental borrowing rate in the assessment of lease classification as capital or operating and defines the initial lease term to include renewal options determined to be reasonably assured.
The Company conducts operations primarily under operating leases.
Many of the Company's real property lease agreements contain incentives for tenant improvements, rent holidays, or rent escalation clauses.
For incentives for tenant improvements, the Company records a deferred rent liability and amortizes the deferred rent over the term of the lease as a reduction to rent expense.
For rent holidays and rent escalation clauses during the lease term, the Company records minimum rental expenses on a straight-line basis over the term of the lease.
For purposes of recognizing lease incentives, the Company uses the date of initial possession as the commencement date, which is generally the date on which the Company is given the right of access to the space and begins to make improvements in preparation for the intended use.
Goodwill and Other Intangible Assets - The Company performs impairment tests for goodwill as of November 30 of each year and between annual impairment tests if evidence of potential impairment exists, by first comparing the carrying value of net assets to the fair value of the related operations.
If the fair value is determined to be less than the carrying value, a second step is performed to determine if goodwill is impaired, by comparing the estimated fair value of goodwill to its carrying value.
Purchased intangible assets are amortized on a straight-line basis or a method based on the pattern of benefits over their estimated useful lives, and the carrying value of these assets is reviewed for impairment when events indicate that a potential impairment may have occurred.
Equity Method Investments - Investments in which the Company has the ability to exercise significant influence over the investee but does not own a majority interest or otherwise control are accounted for under the equity method of accounting and included in other assets in its consolidated statements of financial position.
The Company's equity investments align strategically and are integrated with the Company's operations, and therefore the Company's share of the net earnings or losses of the investee is included in operating income (loss).
The Company evaluates its equity investments for other than temporary impairment whenever events or changes in business circumstances indicate that the carrying amounts of such investments may not be fully recoverable.
If a decline in the value of an equity method investment is determined to be other than temporary, a loss is recorded in earnings in the current period.
Self-Insured Group Medical Insurance - The Company maintains a self-insured group medical insurance plan.
The plan is designed to provide a specified level of coverage for employees and their dependents.
Estimated liabilities

Question: In the year with lowest amount of Service cost, what's the increasing rate of Interest cost for Pension Benefits? (in %)

Solution:
def solution():
    # Define variables name and value
    interest_cost_2015 = 242
    interest_cost_2014 = 253

    # Do math calculation to get the answer
    difference = interest_cost_2015 - interest_cost_2014
    increasing_rate = (difference / interest_cost_2014) * 100
    
    return increasing_rate

Answer: -4.3478260869565215