Note 4: Property, Plant and Equipment The following table summarizes the major classes of property, plant and equipment by category as of December 31:
## Table 0 ##
Property, plant and equipment depreciation expense amounted to $405, $392, and $374 for the years ended December 31, 2015, 2014 and 2013, respectively and was included in depreciation and amortization expense in the accompanying Consolidated Statements of Operations.
The provision for depreciation expressed as a percentage of the aggregate average depreciable asset balances was 3.13% for the year ended December 31, 2015 and 3.20% for years December 31, 2014 and 2013.
Note 5: Allowance for Uncollectible Accounts The following table summarizes the changes in the Company’s allowances for uncollectible accounts for the years ended December 31:
MetLife, Inc.  Notes to the Consolidated Financial Statements — (Continued) Credit Risk on Freestanding Derivatives The Company may be exposed to credit-related losses in the event of nonperformance by counterparties to derivative financial instruments.
Generally, the current credit exposure of the Company’s derivative contracts is limited to the net positive estimated fair value of derivative contracts at the reporting date after taking into consideration the existence of netting agreements and any collateral received pursuant to credit support annexes.
The Company manages its credit risk related to over-the-counter derivatives by entering into transactions with creditworthy counterparties, maintaining collateral arrangements and through the use of master agreements that provide for a single net payment to be made by one counterparty to another at each due date and upon termination.
Because exchange-traded futures are effected through regulated exchanges, and positions are marked to market on a daily basis, the Company has minimal exposure to credit-related losses in the event of nonperformance by counterparties to such derivative instruments.
See Note 1 for a description of the impact of credit risk on the valuation of derivative instruments.
The Company enters into various collateral arrangements, which require both the pledging and accepting of collateral in connection with its derivative instruments.
At December 31, 2009 and 2008, the Company was obligated to return cash collateral under its control of $2,680 million and $7,758 million, respectively.
This unrestricted cash collateral is included in cash and cash equivalents or in short-term investments and the obligation to return it is included in payables for collateral under securities loaned and other transactions in the consolidated balance sheets.
At December 31, 2009 and 2008, the Company had also accepted collateral consisting of various securities with a fair market value of $221 million and $1,249 million, respectively, which are held in separate custodial accounts.
The Company is permitted by contract to sell or repledge this collateral, but at December 31, 2009, none of the collateral had been sold or repledged.
The Company’s collateral arrangements for its over-the-counter derivatives generally require the counterparty in a net liability position, after considering the effect of netting agreements, to pledge collateral when the fair value of that counterparty’s derivatives reaches a predetermined threshold.
Certain of these arrangements also include credit-contingent provisions that provide for a reduction of these thresholds (on a sliding scale that converges toward zero) in the event of downgrades in the credit ratings of the Company and/or the counterparty.
In addition, certain of the Company’s netting agreements for derivative instruments contain provisions that require the Company to maintain a specific investment grade credit rating from at least one of the major credit rating agencies.
If the Company’s credit ratings were to fall below that specific investment grade credit rating, it would be in violation of these provisions, and the counterparties to the derivative instruments could request immediate payment or demand immediate and ongoing full overnight collateralization on derivative instruments that are in a net liability position after considering the effect of netting agreements.
The following table presents the estimated fair value of the Company’s over-the-counter derivatives that are in a net liability position after considering the effect of netting agreements, together with the estimated fair value and balance sheet location of the collateral pledged.
The table also presents the incremental collateral that the Company would be required to provide if there was a one notch downgrade in the Company’s credit rating at the reporting date or if the Company’s credit rating sustained a downgrade to a level that triggered full overnight collateralization or termination of the derivative position at the reporting date.
Derivatives that are not subject to collateral agreements are not included in the scope of this table.
## Table 1 ##
(1) After taking into consideration the existence of netting agreements.
(2) Included in fixed maturity securities in the consolidated balance sheets.
The counterparties are permitted by contract to sell or repledge this collateral.
At December 31, 2009, the Company did not provide any cash collateral.
Without considering the effect of netting agreements, the estimated fair value of the Company’s over-the-counter derivatives with creditcontingent provisions that were in a gross liability position at December 31, 2009 was $1,645 million.
At December 31, 2009, the Company provided securities collateral of $1,017 million in connection with these derivatives.
In the unlikely event that both: (i) the Company’s credit rating is downgraded to a level that triggers full overnight collateralization or termination of all derivative positions; and (ii) the Company’s netting agreements are deemed to be legally unenforceable, then the additional collateral that the Company would be required to provide to its counterparties in connection with its derivatives in a gross liability position at December 31, 2009 would be $628 million.
This amount does not consider gross derivative assets of $488 million for which the Company has the contractual right of offset.
At December 31, 2008, the Company provided securities collateral for various arrangements in connection with derivative instruments of $776 million, which is included in fixed maturity securities.
The counterparties are permitted by contract to sell or repledge this collateral.
The Company also has exchange-traded futures, which require the pledging of collateral.
At December 31, 2009 and 2008, the Company pledged securities collateral for exchange-traded futures of $50 million and $282 million, respectively, which is included in fixed maturity
MetLife, Inc.  Notes to the Consolidated Financial Statements — (Continued) At December 31, 2008, the Company’s total amount of unrecognized tax benefits was $766 million and the total amount of unrecognized tax benefits that would affect the effective tax rate, if recognized, was $567 million.
The total amount of unrecognized tax benefits decreased by $74 million from December 31, 2007 primarily due to settlements reached with the IRS with respect to certain significant issues involving demutualization, leasing and tax credits offset by additions for tax positions of the current year.
As a result of the settlements, items within the liability for unrecognized tax benefits, in the amount of $153 million, were reclassified to current and deferred income tax payable, as applicable, of which $20 million was paid in 2008 and $133 million was paid in 2009.
At December 31, 2009, the Company’s total amount of unrecognized tax benefits was $773 million and the total amount of unrecognized tax benefits that would affect the effective tax rate, if recognized, was $583 million.
The total amount of unrecognized tax benefits increased by $7 million from December 31, 2008 primarily due to additions for tax positions of the current and prior years offset by settlements reached with the IRS.
Settlements with tax authorities amounted to $46 million, of which $44 million was reclassified to current income tax payable and paid in 2009 and $2 million reduced current income tax expense.
The Company’s liability for unrecognized tax benefits may decrease in the next 12 months pending the outcome of remaining issues, taxexempt income and tax credits, associated with the 2000 to 2002 IRS audit.
A reasonable estimate of decrease cannot be made at this time.
However, the Company continues to believe that the ultimate resolution of the issues will not result in a material change to its consolidated financial statements, although the resolution of income tax matters could impact the Company’s effective tax rate for a particular future period.
A reconciliation of the beginning and ending amount of unrecognized tax benefits is as follows:
## Table 2 ##
During the year ended December 31, 2007, the Company recognized $81 million in interest expense associated with the liability for unrecognized tax benefits.
At December 31, 2007, the Company had $218 million of accrued interest associated with the liability for unrecognized tax benefits.
The $8 million increase from January 1, 2007 in accrued interest associated with the liability for unrecognized tax benefits resulted from an increase of $81 million of interest expense and a $73 million decrease primarily resulting from the aforementioned IRS settlements.
The $73 million was reclassified to current income tax payable in 2007 and paid in 2009.
During the year ended December 31, 2008, the Company recognized $37 million in interest expense associated with the liability for unrecognized tax benefits.
At December 31, 2008, the Company had $176 million of accrued interest associated with the liability for unrecognized tax benefits.
The $42 million decrease from December 31, 2007 in accrued interest associated with the liability for unrecognized tax benefits resulted from an increase of $37 million of interest expense and a $79 million decrease primarily resulting from the aforementioned IRS settlements.
Of the $79 million decrease, $78 million was reclassified to current income tax payable in 2008, with $7 million and $71 million paid in 2008 and 2009, respectively.
The remaining $1 million reduced interest expense.
During the year ended December 31, 2009, the Company recognized $44 million in interest expense associated with the liability for unrecognized tax benefits.
At December 31, 2009, the Company had $198 million of accrued interest associated with the liability for unrecognized tax benefits.
The $22 million increase from December 31, 2008 in accrued interest associated with the liability for unrecognized tax benefits resulted from an increase of $44 million of interest expense and a $22 million decrease primarily resulting from the aforementioned IRS settlements.
Of the $22 million decrease, $20 million has been reclassified to current income tax payable and was paid in 2009.
The remaining $2 million reduced interest expense.
The U. S.  Treasury Department and the IRS have indicated that they intend to address through regulations the methodology to be followed in determining the dividends received deduction (“DRD”), related to variable life insurance and annuity contracts.
The DRD reduces the amount of dividend income subject to tax and is a significant component of the difference between the actual tax expense and expected amount determined using the federal statutory tax rate of 35%.
Any regulations that the IRS ultimately proposes for issuance in this area will be subject to public notice and comment, at which time insurance companies and other interested parties will have the opportunity to raise legal and practical questions about the content, scope and application of such regulations.
As a result, the ultimate timing and substance of any such regulations are unknown at this time.
For the years ended December 31, 2009 and 2008, the Company recognized an income tax benefit of $216 million and $179 million, respectively, related to the separate account DRD.
The 2009 benefit included a benefit of $33 million related to a true-up of the prior year tax return.16.
Contingencies, Commitments and Guarantees Contingencies Litigation The Company is a defendant in a large number of litigation matters.
In some of the matters, very large and/or indeterminate amounts, including punitive and treble damages, are sought.
Modern pleading practice in the United States permits considerable variation in the
MetLife, Inc.  Notes to the Consolidated Financial Statements — (Continued) insurer engaged.
Some states permit member insurers to recover assessments paid through full or partial premium tax offsets.
Assets and liabilities held for insolvency assessments are as follows:
## Table 3 ##
(1) The Company holds a receivable from the seller of a prior acquisition in accordance with the purchase agreement.
Assessments levied against the Company were $2 million, $2 million and ($1) million for the years ended December 31, 2009, 2008 and 2007, respectively.
Argentina The Argentine economic, regulatory and legal environment, including interpretations of laws and regulations by regulators and courts, is uncertain.
Potential legal or governmental actions related to pension reform, fiduciary responsibilities, performance guarantees and tax rulings could adversely affect the results of the Company.
In 2007, pension reform legislation in Argentina was enacted which relieved the Company of its obligation to provide death and disability policy coverages and resulted in the elimination of related insurance liabilities.
The reform reinstituted the government’s pension plan system and allowed for pension participants to transfer their future contributions to the government pension plan system.
Although it no longer received compensation, the Company continued to be responsible for managing the funds of those participants that transferred to the government system.
This change resulted in the establishment of a liability for future servicing obligations and the elimination of the Company’s obligations under death and disability policy coverages.
The impact of the 2007 Argentine pension reform was an increase to net income of $114 million, net of income tax, due to the reduction of the insurance liabilities and other balances associated with the death and disability coverages of $197 million, net of income tax, which exceeded the establishment of the liability for future service obligations of $83 million, net of income tax, during the year ended December 31, 2007.
During 2008, the future servicing obligation was reduced by $23 million, net of income tax, when information regarding the level of participation in the government pension plan became fully available.
In September 2008, the Argentine Supreme Court ruled against the validity of the 2002 Pesification Law enacted by the Argentine government.
This ruling applied to certain social security pension annuity contractholders that had filed a lawsuit against the 2002 Pesification Law.
The annuity contracts impacted by this ruling, which were deemed peso denominated under the 2002 Pesification Law, are now considered to be U. S.  Dollar denominated obligations of the Company.
The applicable contingent liabilities were then adjusted and refined to be consistent with this ruling.
The impact of the refinements resulting from the change in these contingent liabilities and the associated future policyholder benefits was an increase to net income of $34 million, net of income tax, during the year ended December 31, 2008.
In October 2008, the Argentine government announced its intention to nationalize private pensions and, in December 2008, the Argentine government nationalized the private pension system seizing the underlying investments of participants which were being managed by the Company (“Nationalization”).
With this action, the Company’s pension business in Argentina ceased to exist and the Company eliminated certain assets and liabilities held in connection with the pension business.
Deferred acquisition costs, deferred tax assets, and liabilities — primarily the liability for future servicing obligation referred to above — were eliminated and the Company incurred severance costs associated with the termination of employees.
The impact of the elimination of assets and liabilities and the incurral of severance costs was an increase to net income of $6 million, net of income tax, during the year ended December 31, 2008.
As part of Nationalization, the Company may receive compensation from the Argentine government for the loss of the pension business in the form of government bonds.
The amount of any such compensation, as well as the terms and value of the government bonds to be received, cannot be determined at this time.
The compensation will only be reflected in the consolidated financial statements of the Company if and when the fair value of the compensation is received.
In March 2009, in light of market developments resulting from the Supreme Court ruling contrary to the Pesification Law and the implementation by the Company of a program to allow the contractholders that had not filed a lawsuit to convert to U. S.  Dollars the social security annuity contracts denominated in pesos by the Pesification Law, the Company further reduced the outstanding contingent liabilities by $108 million, net of income tax, which was partially offset by the establishment of contingent liabilities from the implementation of the program to convert these contracts to U. S.  Dollars of $13 million, net of income tax, resulting in a decrease to net loss of $95 million, net of income tax, for the year ended December 31, 2009.
Further governmental or legal actions are possible in Argentina.
Such actions may impact the level of existing liabilities or may create additional obligations or benefits to the Company’s operations in Argentina.
Management has made its best estimate of its obligations based upon information currently available; however, further governmental or legal actions could result in changes in obligations which could materially impact the amounts presented within the consolidated financial statements.
Proceeds from sales or disposals of fixed maturity and equity securities and the components of fixed maturity and equity securities net investment gains (losses) are as follows:
## Table 4 ##
(1) Other OTTI losses recognized in earnings include impairments on equity securities, impairments on perpetual hybrid securities classified within fixed maturity securities where the primary reason for the impairment was the severity and/or the duration of an unrealized loss position and fixed maturity securities where there is an intent to sell or it is more likely than not that the Company will be required to sell the security before recovery of the decline in estimated fair value.
Overview of Fixed Maturity and Equity Security OTTI Losses Recognized in Earnings.
Impairments of fixed maturity and equity securities were $1.9 billion, $1.7 billion and $97 million for the years ended December 31, 2009, 2008 and 2007, respectively.
Impairments of fixed maturity securities were $1.5 billion, $1.3 billion and $78 million for the years ended December 31, 2009, 2008 and 2007, respectively.
Impairments of equity securities were $400 million, $430 million and $19 million for the years ended December 31, 2009, 2008 and 2007, respectively.
The Company’s credit-related impairments of fixed maturity securities were $1.1 billion, $1.1 billion and $58 million for the years ended December 31, 2009, 2008 and 2007, respectively.
The Company’s three largest impairments totaled $508 million, $528 million and $19 million for the years ended December 31, 2009, 2008 and 2007, respectively.
The Company records OTTI losses charged to earnings as investment losses and adjusts the cost basis of the fixed maturity and equity securities accordingly.
The Company does not change the revised cost basis for subsequent recoveries in value.
The Company sold or disposed of fixed maturity and equity securities at a loss that had an estimated fair value of $10.2 billion, $29.9 billion and $47.1 billion for the years ended December 31, 2009, 2008 and 2007, respectively.
Gross losses excluding impairments for fixed maturity and equity securities were $1.2 million, $1.8 billion and $1.1 billion for the years ended December 31, 2009, 2008 and 2007, respectively.
Explanations of changes in fixed maturity and equity securities impairments are as follows: ?
Year Ended December 31, 2009 compared to the Year Ended December 31, 2008 — Overall OTTI losses recognized in earnings on fixed maturity and equity securities were $1.9 billion for the year ended December 31, 2009 as compared to $1.7 billion in the prior year.
The stress in the global financial markets that caused a significant increase in impairments in 2008 as compared to 2007, continued into 2009.
Significant impairments were incurred in several industry sectors in 2009, including the financial services industry, but to a lesser degree in the financial services industry sector than in 2008.
In 2008 certain financial institutions entered bankruptcy, entered Federal Deposit Insurance Corporation (“FDIC”) receivership or received significant government capital infusions causing 2008 financial services industry impairments to be higher than in 2009.
Of the fixed maturity and equity securities impairments of $1,900 million in 2009, $799 million were concentrated in the Company’s financial services industry holdings and were comprised of $459 million in impairments on fixed maturity securities and $340 million in impairments on equity securities, and the $799 million included $623 million of perpetual hybrid securities, which were comprised of $313 million on securities classified as fixed maturity securities and $310 million on securities classified as non-redeemable preferred stock.
Overall impairments in 2009 were higher due to increased fixed maturity security impairments across several industry sectors as presented in the tables below, which more than offset a reduction in impairments in the financial services industry sector.
Impairments across these several industry sectors increased in 2009 due to increased financial restructurings, bankruptcy filings, ratings downgrades, collateral deterioration or difficult operating environments of the issuers as a result of the challenging economic environment.
Impairments on perpetual hybrid securities in 2009 were a result of deterioration in the credit rating of the issuer to below investment grade and due to a severe and extended unrealized loss position.  ?
Year Ended December 31, 2008 compared to the Year Ended December 31, 2007 — Overall OTTI losses recognized in earnings on fixed maturity and equity securities were $1.7 billion for the year ended December 31, 2008 as compared to $97 million in the prior year.
The significant increase in impairments of fixed maturity and equity securities in 2008 compared to 2007 was a result of the stress in the global financial markets, particularly in the financial services industry causing an increase in financial restructurings, bankruptcy filings, ratings downgrades, or difficult underlying operating environments for the issuers, as well as an increase in the securities that the Company either lacked the intent to hold, or due to extensive credit spread widening, the Company was uncertain of its intent to hold certain fixed maturity securities for a period of time sufficient to allow for recovery of the market value decline.
Of the fixed maturity and equity securities impairments of $1.7 billion in 2008, $1,014 million were concentrated in the Company’s financial services industry securities holdings and were comprised of $673 million in impairments on fixed maturity securities and $341 million in impairments on equity securities, and the $1,014 million included impairments of $154 million of perpetual hybrid securities, which were comprised of $64 million on securities classified as fixed maturity securities and $90 million on securities classified as non-redeemable preferred

<table><tr><td></td><td>2015</td><td>2014</td><td>2013</td></tr><tr><td>Balance as of January 1</td><td>$-35</td><td>$-34</td><td>$-27</td></tr><tr><td>Amounts charged to expense</td><td>-32</td><td>-37</td><td>-27</td></tr><tr><td>Amounts written off</td><td>38</td><td>43</td><td>24</td></tr><tr><td>Recoveries of amounts written off</td><td>-10</td><td>-7</td><td>-4</td></tr><tr><td>Balance as of December 31</td><td>$-39</td><td>$-35</td><td>$-34</td></tr></table>
<table><tr><td></td><td> Estimated   Fair Value -1 of   Derivatives in Net   Liability Position   December 31, 2009</td><td> Estimated   Fair Value of   Collateral   Provided   December 31, 2009</td><td colspan="2"> Fair Value of Incremental Collateral   Provided Upon:</td></tr><tr><td></td><td></td><td></td><td></td><td> Downgrade in the </td></tr><tr><td></td><td></td><td></td><td> One Notch </td><td> Company’s Credit Rating </td></tr><tr><td></td><td></td><td></td><td> Downgrade </td><td> to a Level that Triggers </td></tr><tr><td></td><td></td><td></td><td> in the </td><td> Full Overnight </td></tr><tr><td></td><td></td><td></td><td> Company’s </td><td> Collateralization or </td></tr><tr><td></td><td></td><td> Fixed Maturity </td><td> Credit </td><td> Termination </td></tr><tr><td></td><td></td><td> Securities -2</td><td> Rating</td><td> of the Derivative Position</td></tr><tr><td></td><td colspan="4"> (In millions)</td></tr><tr><td>Derivatives subject to credit-contingent provisions</td><td>$1,163</td><td>$1,017</td><td>$90</td><td>$218</td></tr><tr><td>Derivatives not subject to credit-contingent provisions</td><td>48</td><td>42</td><td>—</td><td>—</td></tr><tr><td>Total</td><td>$1,211</td><td>$1,059</td><td>$90</td><td>$218</td></tr></table>
<table><tr><td></td><td colspan="3">Years Ended December 31,</td></tr><tr><td></td><td>2009</td><td>2008</td><td>2007</td></tr><tr><td></td><td colspan="3">(In millions)</td></tr><tr><td>Balance at beginning of the period</td><td>$766</td><td>$840</td><td>$932</td></tr><tr><td>Additions for tax positions of prior years</td><td>43</td><td>11</td><td>73</td></tr><tr><td>Reductions for tax positions of prior years</td><td>-33</td><td>-51</td><td>-53</td></tr><tr><td>Additions for tax positions of current year</td><td>52</td><td>147</td><td>77</td></tr><tr><td>Reductions for tax positions of current year</td><td>-9</td><td>-22</td><td>-8</td></tr><tr><td>Settlements with tax authorities</td><td>-46</td><td>-153</td><td>-177</td></tr><tr><td>Lapses of statutes of limitations</td><td>—</td><td>-6</td><td>-4</td></tr><tr><td>Balance at end of the period</td><td>$773</td><td>$766</td><td>$840</td></tr></table>
<table><tr><td></td><td colspan="2"> December 31,</td></tr><tr><td></td><td> 2009</td><td> 2008</td></tr><tr><td></td><td colspan="2"> (In millions)</td></tr><tr><td>Other Assets:</td><td></td><td></td></tr><tr><td>Premium tax offset for future undiscounted assessments</td><td>$54</td><td>$50</td></tr><tr><td>Premium tax offsets currently available for paid assessments</td><td>9</td><td>7</td></tr><tr><td>Receivable for reimbursement of paid assessments -1</td><td>4</td><td>7</td></tr><tr><td></td><td>$67</td><td>$64</td></tr><tr><td>Other Liabilities:</td><td></td><td></td></tr><tr><td>Insolvency assessments</td><td>$86</td><td>$83</td></tr></table>
<table><tr><td></td><td colspan="3">Fixed Maturity Securities Years Ended December 31,</td><td colspan="3">Equity Securities Years Ended December 31,</td><td colspan="3">Total Years Ended December 31,</td></tr><tr><td></td><td>2009</td><td>2008</td><td>2007</td><td>2009</td><td>2008</td><td>2007</td><td>2009</td><td>2008</td><td>2007</td></tr><tr><td></td><td colspan="9">(In millions)</td></tr><tr><td>Proceeds</td><td>$38,972</td><td>$62,495</td><td>$78,001</td><td>$950</td><td>$2,107</td><td>$1,112</td><td>$39,922</td><td>$64,602</td><td>$79,113</td></tr><tr><td>Gross investment gains</td><td>947</td><td>858</td><td>554</td><td>134</td><td>440</td><td>226</td><td>1,081</td><td>1,298</td><td>780</td></tr><tr><td>Gross investment losses</td><td>-1,110</td><td>-1,515</td><td>-1,091</td><td>-133</td><td>-263</td><td>-43</td><td>-1,243</td><td>-1,778</td><td>-1,134</td></tr><tr><td>Total OTTI losses recognized in earnings:</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Credit-related</td><td>-1,137</td><td>-1,138</td><td>-58</td><td>—</td><td>—</td><td>—</td><td>-1,137</td><td>-1,138</td><td>-58</td></tr><tr><td>Other -1</td><td>-363</td><td>-158</td><td>-20</td><td>-400</td><td>-430</td><td>-19</td><td>-763</td><td>-588</td><td>-39</td></tr><tr><td>Total OTTI losses recognized in earnings</td><td>-1,500</td><td>-1,296</td><td>-78</td><td>-400</td><td>-430</td><td>-19</td><td>-1,900</td><td>-1,726</td><td>-97</td></tr><tr><td>Net investment gains (losses)</td><td>$-1,663</td><td>$-1,953</td><td>$-615</td><td>$-399</td><td>$-253</td><td>$164</td><td>$-2,062</td><td>$-2,206</td><td>$-451</td></tr></table>

Question: by how much did property , plant and equipment depreciation expense increase from 2013 to 2015?