Table of Contents outcomes of completed trials and the most current information regarding anticipated timing, progression, and related costs of pre-trial activities and trials in the associated litigation.
The amount of legal defense reserves as of December 31, 2013 and December 31, 2012 of approximately $160 million and $260 million, respectively, represents the Company’s best estimate of the minimum amount of defense costs to be incurred in connection with its outstanding litigation; however, events such as additional trials and other events that could arise in the course of its litigation could affect the ultimate amount of legal defense costs to be incurred by the Company.
The Company will continue to monitor its legal defense costs and review the adequacy of the associated reserves and may determine to increase the reserves at any time in the future if, based upon the factors set forth, it believes it would be appropriate to do so.
Environmental Matters The Company and its subsidiaries are parties to a number of proceedings brought under the Comprehensive Environmental Response, Compensation and Liability Act, commonly known as Superfund, and other federal and state equivalents.
These proceedings seek to require the operators of hazardous waste disposal facilities, transporters of waste to the sites and generators of hazardous waste disposed of at the sites to clean up the sites or to reimburse the government for cleanup costs.
The Company has been made a party to these proceedings as an alleged generator of waste disposed of at the sites.
In each case, the government alleges that the defendants are jointly and severally liable for the cleanup costs.
Although joint and several liability is alleged, these proceedings are frequently resolved so that the allocation of cleanup costs among the parties more nearly reflects the relative contributions of the parties to the site situation.
The Company’s potential liability varies greatly from site to site.
For some sites the potential liability is de minimis and for others the final costs of cleanup have not yet been determined.
While it is not feasible to predict the outcome of many of these proceedings brought by federal or state agencies or private litigants, in the opinion of the Company, such proceedings should not ultimately result in any liability which would have a material adverse effect on the financial position, results of operations, liquidity or capital resources of the Company.
The Company has taken an active role in identifying and providing for these costs and such amounts do not include any reduction for anticipated recoveries of cleanup costs from former site owners or operators or other recalcitrant potentially responsible parties.
In management’s opinion, the liabilities for all environmental matters that are probable and reasonably estimable have been accrued and totaled $213 million and $145 million at December 31, 2013 and 2012, respectively.
These liabilities are undiscounted, do not consider potential recoveries from other parties and will be paid out over the periods of remediation for the applicable sites, which are expected to occur primarily over the next 15 years.
Although it is not possible to predict with certainty the outcome of these matters, or the ultimate costs of remediation, management does not believe that any reasonably possible expenditures that may be incurred in excess of the liabilities accrued should exceed $84 million in the aggregate.
Management also does not believe that these expenditures should result in a material adverse effect on the Company’s financial position, results of operations, liquidity or capital resources for any year.11.
Equity The Merck certificate of incorporation authorizes 6,500,000,000 shares of common stock and 20,000,000 shares of preferred stock.
Capital Stock A summary of common stock and treasury stock transactions (shares in millions) is as follows:
## Table 0 ##
(1) Purchases of treasury stock in 2013 include 105 million shares purchased pursuant to an accelerated share repurchase agreement as discussed below.
(2) Issuances primarily reflect activity under share-based compensation plans.
Table of Contents 13.
Pension and Other Postretirement Benefit Plans The Company has defined benefit pension plans covering eligible employees in the United States and in certain of its international subsidiaries.
As a result of plan design changes approved in 2011, beginning on January 1, 2013, active participants in Merck’s primary U. S.  defined benefit pension plans are accruing pension benefits using new cash balance formulas based on age, service, pay and interest.
However, during a transition period from January 1, 2013 through December 31, 2019, participants will earn the greater of the benefit as calculated under the employee’s legacy final average pay formula or their new cash balance formula.
For all years of service after December 31, 2019, participants will earn future benefits under only the cash balance formula.
In addition, the Company provides medical benefits, principally to its eligible U. S.  retirees and their dependents, through its other postretirement benefit plans.
The Company uses December 31 as the year-end measurement date for all of its pension plans and other postretirement benefit plans.
Net Periodic Benefit Cost The net periodic benefit cost for pension and other postretirement benefit plans consisted of the following components:
## Table 1 ##
The increase in net periodic benefit cost for pension and other postretirement benefit plans in 2013 as compared with 2012 is largely attributable to a change in the discount rate.
The net periodic benefit cost attributable to U. S.  pension plans included in the above table was $348 million in 2013, $268 million in 2012 and $406 million in 2011.
In connection with restructuring actions (see Note 3), termination charges were recorded in 2013, 2012 and 2011 on pension and other postretirement benefit plans related to expanded eligibility for certain employees exiting Merck.
Also, in connection with these restructuring activities, curtailments were recorded in 2013, 2012 and 2011 on pension and other postretirement benefit plans.
In addition, settlements were recorded in 2013, 2012 and 2011 on certain domestic and international pension plans.
Table of Contents A reconciliation of the beginning and ending amount of unrecognized tax benefits is as follows:
## Table 2 ##
(1) Amounts reflect the settlements with the IRS and CRA as discussed below.
If the Company were to recognize the unrecognized tax benefits of $3.5 billion at December 31, 2013, the income tax provision would reflect a favorable net impact of $3.3 billion.
The Company is under examination by numerous tax authorities in various jurisdictions globally.
The Company believes that it is reasonably possible that the total amount of unrecognized tax benefits as of December 31, 2013 could decrease by up to $128 million in the next 12 months as a result of various audit closures, settlements or the expiration of the statute of limitations.
The ultimate finalization of the Company’s examinations with relevant taxing authorities can include formal administrative and legal proceedings, which could have a significant impact on the timing of the reversal of unrecognized tax benefits.
The Company believes that its reserves for uncertain tax positions are adequate to cover existing risks or exposures.
Interest and penalties associated with uncertain tax positions amounted to a benefit of $319 million in 2013, $88 million in 2012 and $95 million in 2011.
These amounts reflect the beneficial impacts of various tax settlements, including those discussed below.
Liabilities for accrued interest and penalties were $665 million and $1.2 billion as of December 31, 2013 and 2012, respectively.
In 2013, the Internal Revenue Service (“IRS”) finalized its examination of Schering-Plough’s 2007-2009 tax years.
The Company’s unrecognized tax benefits for the years under examination exceeded the adjustments related to this examination period and therefore the Company recorded a net $165 million tax provision benefit in 2013.
In 2010, the IRS finalized its examination of Schering-Plough’s 2003-2006 tax years.
In this audit cycle, the Company reached an agreement with the IRS on an adjustment to income related to intercompany pricing matters.
This income adjustment mostly reduced NOLs and other tax credit carryforwards.
The Company’s reserves for uncertain tax positions were adequate to cover all adjustments related to this examination period.
Additionally, as previously disclosed, the Company was seeking resolution of one issue raised during this examination through the IRS administrative appeals process.
In 2013, the Company recorded an out-of-period net tax benefit of $160 million related to this issue, which was settled in the fourth quarter of 2012, with final resolution relating to interest owed being reached in the first quarter of 2013.
The Company’s unrecognized tax benefits related to this issue exceeded the settlement amount.
Management has concluded that the exclusion of this benefit is not material to current or prior year financial statements.
As previously disclosed, the Canada Revenue Agency (the “CRA”) had proposed adjustments for 1999 and 2000 relating to intercompany pricing matters and, in July 2011, the CRA issued assessments for other miscellaneous audit issues for tax years 2001-2004.
In 2012, Merck and the CRA reached a settlement for these years that calls for Merck to pay additional Canadian tax of approximately $65 million.
The Company’s unrecognized tax benefits related to these matters exceeded the settlement amount and therefore the Company recorded a net $112 million tax provision benefit in 2012.
A portion of the taxes paid is expected to be creditable for U. S.  tax purposes.
The Company had previously established reserves for these matters.
The resolution of these matters did not have a material effect on the Company’s results of operations, financial position or liquidity.
In 2011, the IRS concluded its examination of Merck’s 2002-2005 federal income tax returns and as a result the Company was required to make net payments of approximately $465 million.
The Company’s unrecognized tax benefits for the years under examination exceeded the adjustments related to this examination period and therefore the Company recorded a net $700 million tax provision benefit in 2011.
This net benefit reflects the decrease of unrecognized tax benefits for the years under examination partially offset by increases to unrecognized tax benefits for years subsequent

<table><tr><td></td><td colspan="2">2013</td><td colspan="2">2012</td><td colspan="2">2011</td></tr><tr><td></td><td>CommonStock</td><td>TreasuryStock</td><td>CommonStock</td><td>TreasuryStock</td><td>CommonStock</td><td>TreasuryStock</td></tr><tr><td>Balance January 1</td><td>3,577</td><td>550</td><td>3,577</td><td>536</td><td>3,577</td><td>495</td></tr><tr><td>Purchases of treasury stock<sup>-1</sup></td><td>—</td><td>139</td><td>—</td><td>62</td><td>—</td><td>58</td></tr><tr><td>Issuances<sup>-2</sup></td><td>—</td><td>-39</td><td>—</td><td>-48</td><td>—</td><td>-17</td></tr><tr><td>Balance December 31</td><td>3,577</td><td>650</td><td>3,577</td><td>550</td><td>3,577</td><td>536</td></tr></table>
<table><tr><td></td><td>Pension Benefits</td><td>Other Postretirement Benefits</td></tr><tr><td>Years Ended December 31</td><td>2013</td><td>2012</td><td>2011</td><td>2013</td><td>2012</td><td>2011</td></tr><tr><td>Service cost</td><td>$682</td><td>$555</td><td>$619</td><td>$102</td><td>$82</td><td>$110</td></tr><tr><td>Interest cost</td><td>665</td><td>661</td><td>718</td><td>107</td><td>121</td><td>141</td></tr><tr><td>Expected return on plan assets</td><td>-1,097</td><td>-970</td><td>-972</td><td>-126</td><td>-136</td><td>-142</td></tr><tr><td>Net amortization</td><td>336</td><td>185</td><td>201</td><td>-50</td><td>-35</td><td>-17</td></tr><tr><td>Termination benefits</td><td>58</td><td>27</td><td>59</td><td>50</td><td>18</td><td>29</td></tr><tr><td>Curtailments</td><td>-23</td><td>-10</td><td>-86</td><td>-11</td><td>-7</td><td>1</td></tr><tr><td>Settlements</td><td>23</td><td>18</td><td>4</td><td>—</td><td>—</td><td>—</td></tr><tr><td>Net periodic benefit cost</td><td>$644</td><td>$466</td><td>$543</td><td>$72</td><td>$43</td><td>$122</td></tr></table>
<table><tr><td></td><td>2013</td><td>2012</td><td>2011</td></tr><tr><td>Balance January 1</td><td>$4,425</td><td>$4,277</td><td>$4,919</td></tr><tr><td>Additions related to current year positions</td><td>320</td><td>496</td><td>695</td></tr><tr><td>Additions related to prior year positions</td><td>177</td><td>58</td><td>145</td></tr><tr><td>Reductions for tax positions of prior years<sup>-1</sup></td><td>-747</td><td>-320</td><td>-1,223</td></tr><tr><td>Settlements</td><td>-603</td><td>-67</td><td>-259</td></tr><tr><td>Lapse of statute of limitations</td><td>-69</td><td>-19</td><td>—</td></tr><tr><td>Balance December 31</td><td>$3,503</td><td>$4,425</td><td>$4,277</td></tr></table>

Question: What is the average amount of Balance December 31 of 2011 CommonStock, and Balance January 1 of 2013 ?
Answer: 4001