damages to natural resources allegedly caused by the discharge of hazardous substances from two former waste disposal sites in New Jersey.
During the fourth quarter, the Company negotiated a settlement of New Jersey’s claims.
Under the terms of the settlement, the company will transfer to the State of New Jersey 150 acres of undeveloped land with groundwater recharge potential, which the Company acquired for purposes of the settlement, and will pay the state’s attorneys’ fees.
Notice of the settlement was published for public comment in December 2007, and no objections were received.
As a result, the Company and the State of New Jersey have signed the formal settlement agreement pursuant to which the Company will transfer title to the property and will be dismissed from the lawsuit, which will continue against the codefendants.
Accrued Liabilities and Insurance Receivables Related to Legal Proceedings The Company complies with the requirements of Statement of Financial Accounting Standards No.5, “Accounting for Contingencies,” and related guidance, and records liabilities for legal proceedings in those instances where it can reasonably estimate the amount of the loss and where liability is probable.
Where the reasonable estimate of the probable loss is a range, the Company records the most likely estimate of the loss, or the low end of the range if there is no one best estimate.
The Company either discloses the amount of a possible loss or range of loss in excess of established reserves if estimable, or states that such an estimate cannot be made.
For those insured matters where the Company has taken a reserve, the Company also records receivables for the amount of insurance that it expects to recover under the Company’s insurance program.
For those insured matters where the Company has not taken a reserve because the liability is not probable or the amount of the liability is not estimable, or both, but where the Company has incurred an expense in defending itself, the Company records receivables for the amount of insurance that it expects to recover for the expense incurred.
The Company discloses significant legal proceedings even where liability is not probable or the amount of the liability is not estimable, or both, if the Company believes there is at least a reasonable possibility that a loss may be incurred.
Because litigation is subject to inherent uncertainties, and unfavorable rulings or developments could occur, there can be no certainty that the Company may not ultimately incur charges in excess of presently recorded liabilities.
A future adverse ruling, settlement, or unfavorable development could result in future charges that could have a material adverse effect on the Company’s results of operations or cash flows in the period in which they are recorded.
The Company currently believes that such future charges, if any, would not have a material adverse effect on the consolidated financial position of the Company, taking into account its significant available insurance coverage.
Based on experience and developments, the Company periodically reexamines its estimates of probable liabilities and associated expenses and receivables, and whether it is able to estimate a liability previously determined to be not estimable and/or not probable.
Where appropriate, the Company makes additions to or adjustments of its estimated liabilities.
As a result, the current estimates of the potential impact on the Company’s consolidated financial position, results of operations and cash flows for the legal proceedings and claims pending against the Company could change in the future.
The Company estimates insurance receivables based on an analysis of its numerous policies, including their exclusions, pertinent case law interpreting comparable policies, its experience with similar claims, and assessment of the nature of the claim, and records an amount it has concluded is likely to be recovered.
The following table shows the major categories of on-going litigation, environmental remediation and other environmental liabilities for which the Company has been able to estimate its probable liability and for which the Company has taken reserves and the related insurance receivables:
## Table 0 ##
For those significant pending legal proceedings that do not appear in the table and that are not the subject of pending settlement agreements, the Company has determined that liability is not probable or the amount of the liability is not estimable, or both, and the Company is unable to estimate the possible loss or range of loss at this time.
The amounts in the preceding table with respect to breast implant and environmental remediation represent the Company’s best estimate of the respective liabilities.
The Company does not believe that there is any single best estimate of the respirator/mask/asbestos liability or the other environmental liabilities shown above, nor that it can reliably estimate the amount or range of amounts by which those liabilities may exceed the reserves the Company has established.
one year volatility, the median of the term of the expected life rolling volatility, the median of the most recent term of the expected life volatility of 3M stock, and the implied volatility on the grant date.
The expected term assumption is based on the weighted average of historical grants.
Restricted Stock and Restricted Stock Units The following table summarizes restricted stock and restricted stock unit activity for the years ended December 31:
## Table 1 ##
As of December 31, 2015, there was $84 million of compensation expense that has yet to be recognized related to nonvested restricted stock and restricted stock units.
This expense is expected to be recognized over the remaining weightedaverage vesting period of 24 months.
The total fair value of restricted stock and restricted stock units that vested during the years ended December 31, 2015, 2014 and 2013 was $166 million, $145 million and $114 million, respectively.
The Company’s actual tax benefits realized for the tax deductions related to the vesting of restricted stock and restricted stock units for the years ended December 31, 2015, 2014 and 2013 was $62 million, $54 million and $43 million, respectively.
Restricted stock units granted under the 3M 2008 Long-Term Incentive Plan generally vest three years following the grant date assuming continued employment.
Dividend equivalents equal to the dividends payable on the same number of shares of 3M common stock accrue on these restricted stock units during the vesting period, although no dividend equivalents are paid on any of these restricted stock units that are forfeited prior to the vesting date.
Dividends are paid out in cash at the vest date on restricted stock units, except for performance shares which do not earn dividends.
Since the rights to dividends are forfeitable, there is no impact on basic earnings per share calculations.
Weighted average restricted stock unit shares outstanding are included in the computation of diluted earnings per share.
Performance Shares Instead of restricted stock units, the Company makes annual grants of performance shares to members of its executive management.
The 2015 performance criteria for these performance shares (organic volume growth, return on invested capital, free cash flow conversion, and earnings per share growth) were selected because the Company believes that they are important drivers of long-term stockholder value.
The number of shares of 3M common stock that could actually be delivered at the end of the three-year performance period may be anywhere from 0% to 200% of each performance share granted, depending on the performance of the Company during such performance period.
Non-substantive vesting requires that expense for the performance shares be recognized over one or three years depending on when each individual became a 3M executive.
Performance shares do not accrue dividends during the performance period.
Therefore, the grant date fair value is determined by reducing the closing stock price on the date of grant by the net present value of dividends during the performance period.
Pension and Postretirement Obligations: 3M has various company-sponsored retirement plans covering substantially all U. S.  employees and many employees outside the United States.
The primary U. S.  defined-benefit pension plan was closed to new participants effective January 1, 2009.
The Company accounts for its defined benefit pension and postretirement health care and life insurance benefit plans in accordance with Accounting Standard Codification (ASC) 715, Compensation — Retirement Benefits, in measuring plan assets and benefit obligations and in determining the amount of net periodic benefit cost.
ASC 715 requires employers to recognize the underfunded or overfunded status of a defined benefit pension or postretirement plan as an asset or liability in its statement of financial position and recognize changes in the funded status in the year in which the changes occur through accumulated other comprehensive income, which is a component of stockholders’ equity.
While the company believes the valuation methods used to determine the fair value of plan assets are appropriate and consistent with other market participants, the use of different methodologies or assumptions to determine the fair value of certain financial instruments could result in a different estimate of fair value at the reporting date.
See Note 11 for additional discussion of actuarial assumptions used in determining pension and postretirement health care liabilities and expenses.
Pension benefits associated with these plans are generally based primarily on each participant’s years of service, compensation, and age at retirement or termination.
The benefit obligation represents the present value of the benefits that employees are entitled to in the future for services already rendered as of the measurement date.
The Company measures the present value of these future benefits by projecting benefit payment cash flows for each future period and discounting these cash flows back to the December 31 measurement date, using the yields of a portfolio of high quality, fixed-income debt instruments that would produce cash flows sufficient in timing and amount to settle projected future benefits.
Historically, the single aggregated discount rate used for each plan’s benefit obligation was also used for the calculation of all net periodic benefit costs, including the measurement of the service and interest costs.
Beginning in 2016, 3M changed the method used to estimate the service and interest cost components of the net periodic pension and other postretirement benefit costs.
The new method measures service cost and interest cost separately using the spot yield curve approach applied to each corresponding obligation.
Service costs are determined based on duration-specific spot rates applied to the service cost cash flows.
The interest cost calculation is determined by applying duration-specific spot rates to the year-by-year projected benefit payments.
The spot yield curve approach does not affect the measurement of the total benefit obligations as the change in service and interest costs offset in the actuarial gains and losses recorded in other comprehensive income.
The Company changed to the new method to provide a more precise measure of service and interest costs by improving the correlation between the projected benefit cash flows and the discrete spot yield curve rates.
The Company accounted for this change as a change in estimate prospectively beginning in the first quarter of 2016.
As a result of the change to the spot yield curve approach, 2016 defined benefit pension and postretirement net periodic benefit cost is expected to decrease by $180 million.
Including this $180 million, 3M expects global defined benefit pension and postretirement expense in 2016 (before settlements, curtailments, special termination benefits and other) to decrease by approximately $320 million pre-tax when compared to 2015.
Using this methodology, the Company determined discount rates for its plans as follow:
## Table 2 ##
Another significant element in determining the Company’s pension expense in accordance with ASC 715 is the expected return on plan assets, which is based on historical results for similar allocations among asset classes.
For the primary U. S.  qualified pension plan, the expected long-term rate of return on an annualized basis for 2016 is 7.50%, 0.25% lower than 2015.
Refer to Note 11 for information on how the 2015 rate was determined.
Return on assets assumptions for

<table><tr><td>At December 31 (Millions)</td><td>2007</td><td>2006</td><td>2005</td></tr><tr><td>Breast implant liabilities</td><td>$1</td><td>$4</td><td>$7</td></tr><tr><td>Breast implant receivables</td><td>64</td><td>93</td><td>130</td></tr><tr><td>Respirator mask/asbestos liabilities</td><td>121</td><td>181</td><td>210</td></tr><tr><td>Respirator mask/asbestos receivables</td><td>332</td><td>380</td><td>447</td></tr><tr><td>Environmental remediation liabilities</td><td>37</td><td>44</td><td>30</td></tr><tr><td>Environmental remediation receivables</td><td>15</td><td>15</td><td>15</td></tr><tr><td>Other environmental liabilities</td><td>147</td><td>14</td><td>8</td></tr></table>
<table><tr><td></td><td colspan="2">2015</td><td colspan="2">2014</td><td colspan="2">2013</td></tr><tr><td></td><td>Number of Awards</td><td>Weighted Average Grant Date Fair Value</td><td>Number of Awards</td><td>Weighted Average Grant Date Fair Value</td><td>Number of Awards</td><td>Weighted Average Grant Date Fair Value</td></tr><tr><td>Nonvested balance —</td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>As of January 1</td><td>2,817,786</td><td>$104.41</td><td>3,105,361</td><td>$92.31</td><td>3,261,562</td><td>$85.17</td></tr><tr><td>Granted</td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Annual</td><td>671,204</td><td>165.86</td><td>798,615</td><td>126.79</td><td>946,774</td><td>101.57</td></tr><tr><td>Other</td><td>26,886</td><td>156.94</td><td>78,252</td><td>152.74</td><td>44,401</td><td>111.19</td></tr><tr><td>Vested</td><td>-1,010,612</td><td>89.99</td><td>-1,100,675</td><td>90.37</td><td>-1,100,095</td><td>79.93</td></tr><tr><td>Forfeited</td><td>-64,176</td><td>118.99</td><td>-63,767</td><td>97.23</td><td>-47,281</td><td>90.82</td></tr><tr><td>As of December 31</td><td>2,441,088</td><td>$127.47</td><td>2,817,786</td><td>$104.41</td><td>3,105,361</td><td>$92.31</td></tr></table>
<table><tr><td></td><td>U.S. Qualified Pension</td><td>International Pension (weighted average)</td><td>U.S. Postretirement Medical</td></tr><tr><td>December 31, 2014 Liability and 2015 Net Periodic Benefit Cost:</td><td></td><td></td><td></td></tr><tr><td>Single discount rate</td><td>4.10%</td><td>3.11%</td><td>4.07%</td></tr><tr><td>December 31, 2015 Liability:</td><td></td><td></td><td></td></tr><tr><td>Benefit obligation</td><td>4.47%</td><td>3.12%</td><td>4.32%</td></tr><tr><td>2016 Net Periodic Benefit Cost Components:</td><td></td><td></td><td></td></tr><tr><td>Service cost</td><td>4.72%</td><td>2.84%</td><td>4.60%</td></tr><tr><td>Interest cost</td><td>3.77%</td><td>2.72%</td><td>3.44%</td></tr></table>

Question: Which year is As of January 1 for Number of Awards the least?
Answer: 2015