Private equity fund investments included above are not redeemable, because distributions from the funds will be received when underlying investments of the funds are liquidated.
Private equity funds are generally expected to have 10-year lives at their inception, but these lives may be extended at the fund manager’s discretion, typically in one or two-year increments.
At December 31, 2016, assuming average original expected lives of 10 years for the funds, 73 percent of the total fair value using net asset value per share (or its equivalent) presented above would have expected remaining lives of three years or less, 10 percent between four and six years and 17 percent between seven and 10 years.
The hedge fund investments included above, which are carried at fair value, are generally redeemable monthly (16 percent), quarterly (37 percent), semi-annually (11 percent) and annually (36 percent), with redemption notices ranging from one day to 180 days.
At December 31, 2016, investments representing approximately 72 percent of the total fair value of these hedge fund investments had partial contractual redemption restrictions.
These partial redemption restrictions are generally related to one or more investments held in the hedge funds that the fund manager deemed to be illiquid.
The majority of these contractual restrictions, which may have been put in place at the fund’s inception or thereafter, have pre-defined end dates.
The majority of these restrictions are generally expected to be lifted by the end of 2017.
FAIR VALUE OPTION Under the fair value option, we may elect to measure at fair value financial assets and financial liabilities that are not otherwise required to be carried at fair value.
Subsequent changes in fair value for designated items are reported in earnings.
We elect the fair value option for certain hybrid securities given the complexity of bifurcating the economic components associated with the embedded derivatives.
Refer to Note 11 for additional information related to embedded derivatives.
Additionally, we elect the fair value option for certain alternative investments when such investments are eligible for this election.
We believe this measurement basis is consistent with the applicable accounting guidance used by the respective investment company funds themselves.
Refer to Note 6 herein for additional information.
The following table presents the gains or losses recorded related to the eligible instruments for which we elected the fair value option:
## Table 0 ##
(a) Includes certain hedge funds, private equity funds and other investment partnerships.
(b) Includes GIAs, notes, bonds and mortgages payable.
Interest income and dividend income on assets measured under the fair value option are recognized and included in Net investment income in the Consolidated Statements of Income with the exception of activity within AIG’s Other Operations category, which is included in Other income.
Interest expense on liabilities measured under the fair value option is reported in Other Income in the Consolidated Statements of Income.
See Note 6 herein for additional information about our policies for recognition, measurement, and disclosure of interest and dividend income.
During 2016, 2015 and 2014, we recognized gains of $22 million, and losses of $4 million and $32 million, respectively, attributable to the observable effect of changes in credit spreads on our own liabilities for which the fair value option was elected.
We calculate the effect of these credit spread changes using discounted cash flow techniques that incorporate current market interest rates, our observable credit spreads on these liabilities and other factors that mitigate the risk of nonperformance such as cash collateral posted.
Defined benefit plan obligations in which the projected benefit obligation was in excess of the related plan assets and the accumulated benefit obligation was in excess of the related plan assets were as follows:
## Table 1 ##
The following table presents the components of net periodic benefit cost with respect to pensions and other postretirement benefits:
## Table 2 ##
The estimated net loss and prior service credit that will be amortized from Accumulated other comprehensive income into net periodic benefit cost over the next fiscal year are $41 million and $0.3 million, respectively, for our combined defined benefit pension plans.
For the defined benefit postretirement plans, the estimated amortization from Accumulated other comprehensive income for net loss and prior service credit that will be amortized into net periodic benefit cost over the next fiscal year is a $0.8 million credit in the aggregate.
As of 2016, interest cost for pension and postretirement benefits for our U. S.  plans and largest non-U.
S.  plans is measured by applying the specific spot rates along the yield curve to the plans’ corresponding discounted cash flows that comprise the obligation (the Spot Rate Approach).
This method provides a more precise measurement of interest cost by aligning the timing of the plans’ discounted cash flows to the corresponding spot rates on the yield curve.
Previously, interest cost was measured utilizing a single weighted-average discount rate derived from the yield curve used to measure the benefit obligations.
A 100 basis point increase in the discount rate or expected long-term rate of return would decrease the 2017 pension expense by approximately $20 million and $45 million, respectively, with all other items remaining the same.
Conversely, a 100 basis point decrease in the discount rate or expected long-term rate of return would increase the 2017 pension expense by approximately $24 million and $45 million, respectively, with all other items remaining the same.
Discount Rate Methodology The projected benefit cash flows under the U. S.  AIG Retirement Plan were discounted using the spot rates derived from the Mercer US Pension Discount Yield Curve at December 31, 2016 and 2015, which resulted in a single discount rate that would produce the same liability at the respective measurement dates.
The discount rates were 4.15 percent at December 31, 2016 and 4.32 percent at December 31, 2015.
The methodology was consistently applied for the respective years in determining the discount rates for the other U. S.  pension plans.
In general, the discount rates for non-U.
S.  pension plans were developed based on the duration of liabilities on a plan by plan basis and were selected by reference to high quality corporate bonds in developed markets or local government bonds where developed markets are not as robust or are nonexistent.
The projected benefit obligation for AIG’s Japan pension plans represents approximately 54 percent and 50 percent of the total projected benefit obligations for our non-U.
S.  pension plans at December 31, 2016 and 2015, respectively.
The weighted average discount rate of 0.47 percent and 0.99 percent at December 31, 2016 and 2015, respectively, was selected by reference to the Mercer Yield Curve (Japan) based on the duration of the plans’ liabilities.
Plan Assets The investment strategy with respect to assets relating to our U. S.  and non-U.
S.  pension plans is designed to achieve investment returns that will provide for the benefit obligations of the plans over the long term, limit the risk of short-term funding shortfalls and maintain liquidity sufficient to address cash needs.
Accordingly, the asset allocation strategy is designed to maximize the investment rate of return while managing various risk factors, including, but not limited to, volatility relative to the benefit obligations, liquidity, diversification and concentration, and incorporates the risk/return profile applicable to each asset class.
There were no shares of AIG Common Stock included in the U. S.  and non-U.
S.  pension plans assets at December 31, 2016 or 2015.
U. S.  Pension Plan The assets of the qualified plan are monitored by the AIG U. S.  Investment Committee and actively managed by the investment managers, which involves allocating the plan’s assets among approved asset classes within ranges as permitted by the strategic allocation.
The long-term strategic asset allocation historically has been reviewed and revised approximately every three years.
Beginning in 2016, the investment strategy focus is on de-risking the Plan via regular monitoring.
This was implemented through liability driven investing and the adoption of the glide path approach, where the glide path defines the target allocation for the “ReturnSeeking” portion of the portfolio (i. e. , growth assets) based on the funded ratio.
Under this approach, the allocation to growth assets is reduced and the allocation to liability-hedging assets is increased as the Plan’s funded ratio increases in accordance with the defined glide path.
The following table presents the asset allocation percentage by major asset class for the U. S.  qualified plan and the target allocation for 2017 based on the plan’s funded status at December 31, 2016:
## Table 3 ##
The expected long-term rate of return for the plan was 7.0 percent and 7.25 percent for 2016 and 2015, respectively.
The expected rate of return is an aggregation of expected returns within each asset class category, weighted for the investment mix of the assets.
The combination of the expected asset return and any contributions made by us are expected to maintain the plan’s ability to meet all required benefit obligations.
The expected asset return for each asset class was developed based on an approach that considers key fundamental drivers of the asset class returns in addition to historical returns, current market conditions, asset volatility and the expectations for future market returns.
Non-U.
S.  Pension Plans The assets of the non-U.
S.  pension plans are held in various trusts in multiple countries and are invested primarily in equities and fixed maturity securities to maximize the long-term return on assets for a given level of risk.
During fiscal 2006, we repurchased 19 million shares of common stock for an aggregate purchase price of $892 million, of which $7 million settled after the end of our fiscal year.
In fiscal 2005, we repurchased 17 million shares of common stock for an aggregate purchase price of $771 million.
A total of 146 million shares were held in treasury at May 28, 2006.
We also used cash from operations to repay $189 million in outstanding debt in fiscal 2006.
In fiscal 2005, we repaid nearly $2.2 billion of debt, including the purchase of $760 million principal amount of our 6 percent notes due in 2012.
Fiscal 2005 debt repurchase costs were $137 million, consisting of $73 million of noncash interest rate swap losses reclassified from Accumulated Other Comprehensive Income, $59 million of purchase premium and $5 million of noncash unamortized cost of issuance expense.
Capital Structure

<table><tr><td> Years Ended December 31,</td><td colspan="3">Gain (Loss)</td></tr><tr><td><i>(in millions)</i></td><td>2016</td><td>2015</td><td>2014</td></tr><tr><td> Assets:</td><td></td><td></td><td></td></tr><tr><td>Bond and equity securities</td><td>$447</td><td>$616</td><td>$2,099</td></tr><tr><td>Alternative investments<sup>(a)</sup></td><td>28</td><td>36</td><td>313</td></tr><tr><td>Other, including Short-term investments</td><td>-</td><td>2</td><td>10</td></tr><tr><td> Liabilities:</td><td></td><td></td><td></td></tr><tr><td>Long-term debt<sup>(b)</sup></td><td>-9</td><td>-38</td><td>-269</td></tr><tr><td>Other liabilities</td><td>-</td><td>-3</td><td>-13</td></tr><tr><td> Total gain</td><td>$466</td><td>$613</td><td>$2,140</td></tr></table>
<table><tr><td> At December 31,</td><td colspan="4">PBO Exceeds Fair Value of Plan Assets</td><td colspan="4">ABO Exceeds Fair Value of Plan Assets</td></tr><tr><td><i>(in millions)</i></td><td>U.S. Plans 2016</td><td>2015</td><td>Non-U.S. Plans 2016</td><td>2015</td><td>U.S. Plans 2016</td><td>2015</td><td>Non-U.S. Plans 2016</td><td>2015</td></tr><tr><td>Projected benefit obligation</td><td>$4,948</td><td>$5,324</td><td>$1,121</td><td>$999</td><td>$4,948</td><td>$5,324</td><td>$1,029</td><td>$912</td></tr><tr><td>Accumulated benefit obligation</td><td>4,948</td><td>5,324</td><td>1,016</td><td>896</td><td>4,948</td><td>5,324</td><td>1,009</td><td>889</td></tr><tr><td>Fair value of plan assets</td><td>3,843</td><td>4,359</td><td>545</td><td>506</td><td>3,843</td><td>4,359</td><td>536</td><td>497</td></tr></table>
<table><tr><td> Years Ended December 31,</td><td colspan="6">Pension</td><td colspan="6">Postretirement</td></tr><tr><td></td><td colspan="3">U.S. Plans</td><td colspan="3">Non-U.S. Plans</td><td colspan="3">U.S. Plans</td><td colspan="3">Non-U.S. Plans</td></tr><tr><td><i>(in millions)</i></td><td>2016</td><td>2015</td><td>2014</td><td>2016</td><td>2015</td><td>2014</td><td>2016</td><td>2015</td><td>2014</td><td>2016</td><td>2015</td><td>2014</td></tr><tr><td> Components of net periodic benefit</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td> cost:</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Service cost</td><td>$19</td><td>$192</td><td>$173</td><td>$31</td><td>$43</td><td>$42</td><td>$2</td><td>$5</td><td>$4</td><td>$3</td><td>$3</td><td>$2</td></tr><tr><td>Interest cost</td><td>181</td><td>220</td><td>228</td><td>21</td><td>25</td><td>29</td><td>7</td><td>8</td><td>9</td><td>3</td><td>3</td><td>2</td></tr><tr><td>Expected return on assets</td><td>-292</td><td>-295</td><td>-288</td><td>-26</td><td>-25</td><td>-22</td><td>-</td><td>-</td><td>-</td><td>-</td><td>-</td><td>-</td></tr><tr><td>Amortization of prior service credit</td><td>-</td><td>-22</td><td>-33</td><td>-</td><td>-2</td><td>-3</td><td>-12</td><td>-11</td><td>-11</td><td>-</td><td>-1</td><td>-</td></tr><tr><td>Amortization of net (gain) loss</td><td>25</td><td>92</td><td>42</td><td>7</td><td>9</td><td>7</td><td>-1</td><td>-</td><td>-</td><td>1</td><td>-</td><td>-</td></tr><tr><td>Curtailment (gain) loss</td><td>-</td><td>-179</td><td>-</td><td>-6</td><td>-1</td><td>1</td><td>-1</td><td>-</td><td>-</td><td>-</td><td>-</td><td>-</td></tr><tr><td>Settlement loss</td><td>149</td><td>-</td><td>-</td><td>2</td><td>1</td><td>-</td><td>-</td><td>-</td><td>-</td><td>-</td><td>-</td><td>-</td></tr><tr><td> Net periodic benefit cost (credit)</td><td>$82</td><td>$8</td><td>$122</td><td>$29</td><td>$50</td><td>$54</td><td>$-5</td><td>$2</td><td>$2</td><td>$7</td><td>$5</td><td>$4</td></tr><tr><td> Total recognized in Accumulated other</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td> comprehensive income (loss)</td><td>$-82</td><td>$143</td><td>$-793</td><td>$-101</td><td>$38</td><td>$-40</td><td>$-7</td><td>$12</td><td>$-21</td><td>$1</td><td>$-9</td><td>$-11</td></tr><tr><td> Total recognized in net periodic benefit</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td> cost and other comprehensive</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td> income (loss)</td><td>$-164</td><td>$135</td><td>$-915</td><td>$-130</td><td>$-12</td><td>$-94</td><td>$-2</td><td>$10</td><td>$-23</td><td>$-6</td><td>$-14</td><td>$-15</td></tr></table>
<table><tr><td> At December 31,</td><td>Target 2017</td><td>Actual 2016</td><td>Actual 2015</td></tr><tr><td> Asset class:</td><td></td><td></td><td></td></tr><tr><td>Equity securities</td><td>45%</td><td>43%</td><td>35%</td></tr><tr><td>Fixed maturity securities</td><td>40%</td><td>36%</td><td>41%</td></tr><tr><td>Other investments</td><td>15%</td><td>21%</td><td>24%</td></tr><tr><td> Total</td><td>100%</td><td>100%</td><td>100%</td></tr></table>

Question: What's the difference of Service cost between 2015 and 2016? (in million)
Answer: -188