CELANESE CORPORATION AND SUBSIDIARIES NOTES TO CONSOLIDATED FINANCIAL STATEMENTS (Continued) Included in the pension obligations above are accrued liabilities relating to supplemental retirement plans for certain employees amounting to $235 million and $238 million as of December 31, 2005 and 2004, respectively.
Pension expense relating to these plans included in net periodic benefit cost totaled $15 million, $11 million, $5 million and $18 million for the year ended December 31, 2005, the nine months ended December 31, 2004, the three months ended March 31, 2004 and for the year ended December 31, 2003, respectively.
To fund these obligations, non-qualified trusts were established, included within other non-current assets, which held marketable securities valued at $181 million and $127 million at December 31, 2005 and 2004, respectively, and recognized income (loss), excluding appreciation of insurance contracts, of $6 million, $6 million, $(1) million and $3 million for the year ended December 31, 2005, the nine months ended December 31, 2004, the three months ended March 31, 2004 and the year ended December 31, 2003, respectively.
In addition to holding marketable securities, the nonqualified trust holds investments in insurance contracts of $68 million as of December 31, 2005 and 2004, respectively.
In 2005, the Successor contributed $9 million to these trusts from proceeds received from the demutualization of an insurance company.
In 2003, the Predecessor contributed $18 million to these trusts from proceeds received from the demutualization of an insurance company.
The gain associated with these proceeds was included within Other income (expense), net, in the consolidated statement of operations.
The asset allocation for the qualified U. S.  defined benefit pension plan as of December 31, 2005 and 2004, respectively, and the target allocation ranges for 2006 by asset category is presented below.
The fair value of plan assets for this plan was $2,222 million and $2,199 million as of December 31, 2005 and 2004, respectively.
These asset amounts represent approximately 85% of the total pension assets at December 31, 2005 and 88% at December 31, 2004.
The expected long-term rate of return on these assets was 8.5% at December 31, 2005 and 2004, respectively.
Plan assets did not include any investment in Celanese Corporation common shares during the periods presented.
## Table 0 ##
The asset allocation for the Canadian defined benefit pension plans as of December 31, 2005 and 2004, respectively, and the target allocation ranges for 2006 by asset category are presented below.
The fair value of plan assets for these plans was $198 million and $146 million as of December 31, 2005 and 2004, respectively
The Company’s postretirement benefit plans are unfunded.
The financial objectives of the qualified U. S.  and Canadian pension plans are established in conjunction with a comprehensive review of each plan’s liability structure.
The Company’s asset allocation policy is based on a detailed asset/liability analysis.
In developing investment policy and financial goals,
tax-qualified defined contribution 401(k) savings plans.
Substantially all U. S.  salaried and certain hourly employees are eligible to participate and may make elective deferrals to such plans to save for retirement.
International Paper makes matching contributions to participant accounts on a specified percentage of employee deferrals as determined by the provisions of each plan.
For eligible employees hired after June 30, 2004, the Company makes Retirement Savings Account contributions equal to a percentage of an eligible employee’s pay.
In connection with the Temple-Inland acquisition, International Paper acquired two savings plans which were merged into the International Paper savings plans on December 31, 2012.
The Company also sponsors the International Paper Company Deferred Compensation Savings Plan, which is an unfunded nonqualified defined contribution plan.
This plan permits eligible employees to continue to make deferrals and receive company matching contributions when their contributions to the International Paper Salaried Savings Plan are stopped due to limitations under U. S.  tax law.
Participant deferrals and company matching contributions are not invested in a separate trust, but are paid directly from International Paper’s general assets at the time benefits become due and payable.
Company matching contributions to the plans totaled approximately $112 million, $120 million and $122 million for the plan years ending in 2014, 2013 and 2012, respectively.
NOTE 17 POSTRETIREMENT BENEFITS U. S.  POSTRETIREMENT BENEFITS International Paper provides certain retiree health care and life insurance benefits covering certain U. S.  salaried and hourly employees.
These employees are generally eligible for benefits upon retirement and completion of a specified number of years of creditable service.
Excluded from company-provided medical benefits are salaried employees whose age plus years of employment with the Company totaled less than 60 as of January 1, 2004.  International Paper does not fund these benefits prior to payment and has the right to modify or terminate certain of these plans in the future.
In addition to the U. S.  plan, certain Brazilian and Moroccan employees are eligible for retiree health care and life insurance benefits.
The components of postretirement benefit expense in 2014, 2013 and 2012 were as follows:
## Table 1 ##
(a) Excludes $7 million of curtailment gains in 2013 related to the sale of Building Products that were recorded in Net (gains) losses on sales and impairments of businesses in the consolidated statement of operations.
International Paper evaluates its actuarial assumptions annually as of December 31 (the measurement date) and considers changes in these long-term factors based upon market conditions and the requirements of employers’ accounting for postretirement benefits other than pensions.
Temple-Inland's postretirement plan was remeasured on July 19, 2013 due to the sale of Building Products which reduced the obligation by $6 million.
International Paper's postretirement plan was remeasured on January 31, 2012 due to a negative plan amendment which reduced our obligation by $29 million and reduced the 2012 expected benefit cost by $11 million.
Temple-Inland's postretirement plan was remeasured on July 31, 2012 due to a negative plan amendment which reduced the obligation by $6 million and reduced 2012 expense by $1 million.
The discount rates used to determine net U. S.  and nonU.
S.  postretirement benefit cost for the years ended December 31, 2014, 2013 and 2012 were as follows:
## Table 2 ##
McKESSON CORPORATION FINANCIAL REVIEW (Continued) 46 Historically, we have provided contributions for our profit sharing investment plan (“PSIP”) for U. S.  employees primarily through a leveraged employee stock ownership plan (“ESOP”).
At March 31, 2008, almost all of the 24 million common shares in the ESOP had been allocated to plan participants.
In 2008, 2007 and 2006, we granted 1 million shares per year to plan participants.
As a result, we will need to fund most of our future PSIP contributions with cash or treasury shares.
In 2008, had we paid cash for our PSIP contributions, such contributions would have amounted to $53 million.
Selected Measures of Liquidity and Capital Resources:
## Table 3 ##
(1) Ratio is computed as total debt divided by total debt and stockholders’ equity.
(2) Ratio is computed as total debt, net of cash and cash equivalents (“net debt”), divided by net debt and stockholders’ equity (“net capital employed”).
(3) Ratio is computed as net income, divided by a five-quarter average of stockholders’ equity.
As of March 31, 2008, a significant portion of our cash and cash equivalents are on deposit with foreign financial institutions and are used to fund operations.
Working capital primarily includes cash, receivables and inventories, net of drafts and accounts payable and other liabilities.
Our Distribution Solutions segment requires a substantial investment in working capital that is susceptible to large variations during the year as a result of inventory purchase patterns and seasonal demands.
Inventory purchase activity is a function of sales activity and new customer build-up requirements.
Consolidated working capital at March 31, 2008 decreased compared with that of the prior year end.
Working capital was negatively impacted by decreases in cash and cash equivalents and net financial inventory (inventory, net of drafts and accounts payable) as well as an increase in other accrued liabilities.
These decreases in working capital were partially offset by an increase in account receivables and the one-time benefit associated with a $420 million reclassification of short-term tax liabilities to long-term liabilities as a result of our implementation of FIN No.48.
In 2007, our working capital decreased primarily as a result of increases in other liabilities and deferred revenue.
Net financial inventory resulted in a small increase to working capital in 2007.
Our ratio of net debt to net capital employed increased in 2008 primarily reflecting an increase in net debt (i. e. , a decrease in cash and cash equivalents as well as long-term debt).
Our ratio of net debt to net capital employed increased in 2007 primarily due to our issuance of $1.0 billion of long-term debt in relation to the Per-Se acquisition.
The Company has paid quarterly cash dividends at the rate of $0.06 per share on its common stock since the fourth quarter of 1999.
A dividend of $0.06 per share was declared by the Board on January 23, 2008, and was paid on April 1, 2008 to stockholders of record at the close of business on March 3, 2008.
In 2008, we paid total cash dividends of $70 million.
The Company anticipates that it will continue to pay quarterly cash dividends in the future.
In April 2008, the Board approved a change in the Company’s dividend policy by increasing the amount of the Company’s quarterly dividend from six cents to twelve cents per share, which will apply to ensuing quarterly dividend declarations until further action by the Board.
However, the payment and amount of future dividends remain within the discretion of the Board and will depend upon the Company’s future earnings, financial condition, capital requirements and other factors.
Drilling Activity—The results of crude oil and natural gas wells drilled and completed for each of the last three years were as follows:
## Table 4 ##
(1) Does not include wells drilled but not yet completed.
A productive well is an exploratory or a development well that is not a dry well.
A dry well (hole) is an exploratory or a development well found to be incapable of producing either oil or gas in sufficient quantities to justify completion as an oil or gas well.
An exploratory well is a well drilled to find and produce crude oil or natural gas in an unproved area, to find a new reservoir in a field previously found to be productive of crude oil or natural gas in another reservoir, or to extend a known reservoir.
A development well, for purposes of the table above and as defined in the rules and regulations of the SEC, is a well drilled within the proved area of a crude oil or natural gas reservoir to the depth of a stratigraphic horizon known to be productive.
The number of wells drilled refers to the number of wells completed at any time during the respective year, regardless of when drilling was initiated.
Completion refers to the installation of permanent equipment for the production of crude oil or natural gas, or in the case of a dry hole, to the reporting of abandonment to the appropriate agency.
In addition to the wells drilled and completed during 2007 included in the table above, at December 31, 2007, we were drilling or completing 2 gross (1.0 net) development wells offshore US, 223 gross (192.3 net) development wells and 4 gross (3.3 net) exploratory wells onshore US and one gross (0.1 net) development well in Argentina.
Marketing Activities—We seek opportunities to enhance the value of our US natural gas production by marketing directly to end-users and aggregating natural gas to be sold to natural gas marketers and pipelines.
We also engage in the purchase and sale of third-party crude oil and natural gas production.
Such third-party production may be purchased from non-operators who own working interests in our wells or from other producers’ properties in which we own no interest.
Natural gas produced in the US is sold predominately under short-term or long-term contracts at market-based prices.
In Equatorial Guinea and Israel, we sell natural gas to end-users under long-term contracts at negotiated prices.
During 2007, approximately 12% of natural gas sales were made pursuant to long-term contracts.
Crude oil and condensate produced in the US and foreign locations is generally sold under short-term contracts at market-based prices adjusted for location and quality.
In China, we sell crude oil into the local market under a longterm contract at market-based prices.
Crude oil and condensate are distributed through pipelines and by trucks or tankers to gatherers, transportation companies and refineries.

<table><tr><td></td><td rowspan="2">TargetAllocation 2006</td><td colspan="2">Percentage of Plan Assets atDecember31,</td></tr><tr><td>Asset Category –US</td><td>2005</td><td>2004</td></tr><tr><td>Equitysecurities</td><td>55 - 75%</td><td>77%</td><td>73%</td></tr><tr><td>Debtsecurities</td><td>25 - 35%</td><td>22%</td><td>22%</td></tr><tr><td>Realestate and other</td><td>0 - 15%</td><td>1%</td><td>5%</td></tr><tr><td>Total</td><td></td><td>100%</td><td>100%</td></tr></table>
<table><tr><td>In millions</td><td></td><td rowspan="2">2014 Non- U.S. Plans</td><td></td><td rowspan="2">2013 Non-U.S.Plans</td><td></td><td rowspan="2">2012 Non-U.S.Plans</td></tr><tr><td></td><td>U.S. Plans</td><td>U.S. Plans</td><td>U.S. Plans</td></tr><tr><td>Service cost</td><td>$1</td><td>$1</td><td>$2</td><td>$2</td><td>$3</td><td>$—</td></tr><tr><td>Interest cost</td><td>14</td><td>6</td><td>14</td><td>5</td><td>20</td><td>1</td></tr><tr><td>Actuarial loss</td><td>5</td><td>1</td><td>7</td><td>—</td><td>10</td><td>—</td></tr><tr><td>Amortization of prior service credits</td><td>-13</td><td>-1</td><td>-24</td><td>—</td><td>-30</td><td>—</td></tr><tr><td>Curtailment gain</td><td>—</td><td>—</td><td>—</td><td>—</td><td>-7</td><td>—</td></tr><tr><td>Net postretirement (benefit) expense (a)</td><td>$7</td><td>$7</td><td>$-1</td><td>$7</td><td>$-4</td><td>$1</td></tr></table>
<table><tr><td></td><td>U.S. Plans</td><td>2014 Non- U.S. Plans</td><td>U.S. Plans</td><td>2013 Non- U.S. Plans</td><td>U.S. Plans</td><td>2012 Non-U.S.Plans</td></tr><tr><td>Discount rate</td><td>4.50%</td><td>11.94%</td><td>3.70%</td><td>8.43%</td><td>4.40%</td><td>7.73%</td></tr></table>
<table><tr><td></td><td colspan="3">March 31,</td></tr><tr><td><i>(Dollars in millions)</i></td><td>2008</td><td>2007</td><td>2006</td></tr><tr><td>Cash and cash equivalents</td><td>$1,362</td><td>$1,954</td><td>$2,139</td></tr><tr><td>Working capital</td><td>2,438</td><td>2,730</td><td>3,527</td></tr><tr><td>Debt, net of cash and cash equivalents</td><td>435</td><td>4</td><td>-1,148</td></tr><tr><td>Debt to capital ratio<sup>-1</sup></td><td>22.7%</td><td>23.8%</td><td>14.4%</td></tr><tr><td>Net debt to net capital employed<sup>-2</sup></td><td>6.6%</td><td>0.1%</td><td>-24.1%</td></tr><tr><td>Return on stockholders’ equity<sup>-3</sup></td><td>15.6%</td><td>15.2%</td><td>13.1%</td></tr></table>
<table><tr><td></td><td colspan="3">Net Exploratory Wells</td><td colspan="3">Net Development Wells</td></tr><tr><td></td><td>Productive</td><td>Dry</td><td>Total</td><td>Productive-1</td><td>Dry</td><td>Total</td></tr><tr><td>Year Ended December 31, 2007</td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>United States</td><td>14.2</td><td>4.5</td><td>18.7</td><td>757.6</td><td>27.6</td><td>785.2</td></tr><tr><td>West Africa</td><td>2.6</td><td>0.5</td><td>3.1</td><td>-</td><td>-</td><td>-</td></tr><tr><td>North Sea</td><td>0.5</td><td>-</td><td>0.5</td><td>-</td><td>-</td><td>-</td></tr><tr><td>Israel</td><td>-</td><td>-</td><td>-</td><td>0.4</td><td>-</td><td>0.4</td></tr><tr><td>Argentina</td><td>-</td><td>0.1</td><td>0.1</td><td>6.7</td><td>-</td><td>6.7</td></tr><tr><td>Total</td><td>17.3</td><td>5.1</td><td>22.4</td><td>764.7</td><td>27.6</td><td>792.3</td></tr><tr><td>Year Ended December 31, 2006</td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>United States</td><td>6.3</td><td>9.0</td><td>15.3</td><td>666.6</td><td>5.5</td><td>672.1</td></tr><tr><td>West Africa</td><td>-</td><td>0.4</td><td>0.4</td><td>1.8</td><td>-</td><td>1.8</td></tr><tr><td>North Sea</td><td>-</td><td>-</td><td>-</td><td>1.1</td><td>-</td><td>1.1</td></tr><tr><td>Argentina</td><td>-</td><td>-</td><td>-</td><td>7.6</td><td>-</td><td>7.6</td></tr><tr><td>Total</td><td>6.3</td><td>9.4</td><td>15.7</td><td>677.1</td><td>5.5</td><td>682.6</td></tr><tr><td>Year Ended December 31, 2005</td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>United States</td><td>4.7</td><td>10.7</td><td>15.4</td><td>488.1</td><td>25.9</td><td>514.0</td></tr><tr><td>West Africa</td><td>-</td><td>-</td><td>-</td><td>0.3</td><td>-</td><td>0.3</td></tr><tr><td>North Sea</td><td>-</td><td>0.2</td><td>0.2</td><td>-</td><td>-</td><td>-</td></tr><tr><td>Argentina</td><td>-</td><td>-</td><td>-</td><td>7.7</td><td>-</td><td>7.7</td></tr><tr><td>Total</td><td>4.7</td><td>10.9</td><td>15.6</td><td>496.1</td><td>25.9</td><td>522.0</td></tr></table>

Question: Which year is the amount of the total Net Exploratory Wells in terms of Dry the least?
Answer: 2007