(3) Refer to Note 2 “Summary of Significant Accounting Principles and Practices ” for further information.13.
Employee Benefits p y Defined Contribution Savings Plans Aon maintains defined contribution savings plans for the benefit of its employees.
The expense recognized for these plans is included in Compensation and benefits in the Consolidated Statements of Income.
The expense for the significant plans in the U. S. , U. K. , Netherlands and Canada is as follows (in millions):
## Table 0 ##
Pension and Other Postretirement Benefits The Company sponsors defined benefit pension and postretirement health and welfare plans that provide retirement, medical, and life insurance benefits.
The postretirement health care plans are contributory, with retiree contributions adjusted annually, aand the life insurance and pension plans are generally noncontributory.
The significant U. S. , U. K. , Netherlands and Canadian pension plans are closed to new entrants.
The following table summarizes the major components of our operating expenses, including the impact of foreign currency translation, for the years ended December 31 (dollars in millions):
## Table 1 ##
Significant changes in our operating expenses are discussed below.
‰ Labor and related benefits — Significant items affecting the comparability of expenses for the periods presented include: ‰ Higher wages due to merit increases effective in the second quarter of 2013 and the effect of acquisitions, particularly the Greenstar acquisition in 2013; ‰ Incentive compensation expense fluctuations due to higher anticipated payouts for 2013 as compared to the prior year period and lower payouts for 2012 as compared to 2011; ‰ Increased contract labor in both 2013 and 2012 principally attributed to the recycling line of business; ‰ Headcount, exclusive of acquisitions, decreased in 2013 compared to the prior year period; conversely, headcount increased in 2012 when compared to 2011; and ‰ Non-cash charges incurred during the third quarter of 2013 and the second quarter of 2012 as a result of our partial withdrawals from underfunded multiemployer pension plans.
‰ Maintenance and repairs — The increase in 2013 compared to 2012 was driven by (i) the Greenstar acquisition and (ii) higher internal shop labor costs due in part to higher incentive compensation and merit increases.
The increase in 2012 as compared to 2011 is primarily due to (i) increased fleet maintenance costs, which include services provided by third-parties, tires, parts and internal shop labor costs and (ii) differences in the timing and scope of planned maintenance projects at our waste-to-energy facilities.
‰ Subcontractor costs — The decrease in 2013 was driven primarily by the volume decline associated with the loss of certain strategic accounts.
These decreases were offset, in part, by higher costs associated with the acquired RCI operations.
The increase in 2012 was driven in part by (i) the acquisition of Oakleaf in July 2011 and (ii) increased volumes related to Hurricane Sandy.
‰ Cost of goods sold — The increase in cost of goods sold in 2013 is due in large part to higher customer rebates resulting from higher volumes in our recycling commodity business driven primarily by the acquired Greenstar operations.
The significantly reduced market prices for recyclable commodities in 2012 drove the majority of the cost decrease when compared to the prior period.
‰ Fuel — The decrease in fuel expense in 2013 compared to 2012 was due to (i) a retroactive CNG fuel excise tax credit recognized in the first quarter of 2013; (ii) reduced fuel purchases due to reduced collection volumes; (iii) lower costs as we convert our fleet to CNG vehicles and (iv) lower diesel fuel prices.
The increase in fuel expense in 2012 compared to 2011 was mainly driven by higher diesel fuel prices.
Labor and related benefits — Factors affecting the year-over-year changes in our labor and related benefits costs include: ‰ Higher incentive compensation costs of $94 million in 2013 and $73 million in 2011, as compared with 2012, as a result of higher anticipated payouts.
‰ Higher non-cash compensation expense recognized in 2013 as compared to 2012, in part due to the payout of performance share units granted in 2010, which was approved in 2013.
Expense associated with these awards had been reversed in 2012 when it no longer appeared probable that threshold performance would be achieved.
‰ Cost savings of $45 million in 2013 driven primarily from our July 2012 restructuring.
Professional fees — Consulting fees declined year over year as company-wide initiatives, which began in 2011, were implemented; partially offset by higher legal fees in 2012 as compared with 2013 and 2011.
Provision for bad debts — Our provision for bad debts decreased in 2013 as a result of the collection of certain fully reserved receivables related to our Puerto Rico operations.
Additionally, many of the billing delay issues we experienced throughout fiscal year 2012 with certain of our strategic account customers have been resolved, favorably affecting our year-over-year bad debt comparisons.
Other — In 2013, controllable costs associated with (i) building and equipment; (ii) advertising; (iii) computer and telecommunication; (iv) travel and entertainment and (v) seminars and education have declined primarily as a result of our July 2012 restructuring and continued focus on cost-control initiatives.
In 2012, we experienced decreases in (i) litigation settlement costs and (ii) insurance and claims.
These decreases were partially offset by increases in (i) computer and telecommunications costs, due in part to improvements we are making to our information technology systems and (ii) building and equipment costs, which include rental and utilities.
Depreciation and Amortization Depreciation and amortization includes (i) depreciation of property and equipment, including assets recorded for capital leases, on a straight-line basis from three to 50 years; (ii) amortization of landfill costs, including those incurred and all estimated future costs for landfill development, construction and asset retirement costs arising from closure and post-closure, on a units-of-consumption method as landfill airspace is consumed over the total estimated remaining capacity of a site, which includes both permitted capacity and expansion capacity that meets our Company-specific criteria for amortization purposes; (iii) amortization of landfill asset retirement costs arising from final capping obligations on a units-of-consumption method as airspace is consumed over the estimated capacity associated with each final capping event and (iv) amortization of intangible assets with a definite life, using either a 150% declining balance approach or a straight-line basis over the definitive terms of the related agreements, which are generally from two to 15 years depending on the type of asset.
The following table summarizes the components of our depreciation and amortization costs for the years ended December 31 (dollars in millions):
## Table 2 ##
WASTE MANAGEMENT, INC.  NOTES TO CONSOLIDATED FINANCIAL STATEMENTS — (Continued) not anticipate that the final resolution of the Central States Pension Plan matter could be material to the Company’s business, financial condition or liquidity; however, such loss could have a material adverse effect on our cash flows and, to a lesser extent, our results of operations, for a particular reporting period.
Similarly, we also do not believe that any future withdrawals, individually or in the aggregate, from the multiemployer pension plans to which we contribute, could have a material adverse effect on our business, financial condition or liquidity.
However, such withdrawals could have a material adverse effect on our results of operations or cash flows for a particular reporting period, depending on the number of employees withdrawn in any future period and the financial condition of the multiemployer pension plan(s) at the time of such withdrawal(s).
Tax Matters — We are currently in the examination phase of IRS audits for the tax years 2013 and 2014 and expect these audits to be completed within the next 15 and 27 months, respectively.
We participate in the IRS’s Compliance Assurance Process, which means we work with the IRS throughout the year in order to resolve any material issues prior to the filing of our annual tax return.
We are also currently undergoing audits by various state and local jurisdictions for tax years that date back to 2005, with the exception of affirmative claims in one jurisdiction that date back to 2000.
We are not currently under audit in Canada and, due to the expiration of statutes of limitations, all tax years prior to 2009 are closed.
In July 2011, we acquired Oakleaf, which is subject to potential IRS examinations for the years 2010 and 2011.
Pursuant to the terms of our acquisition of Oakleaf, we are entitled to indemnification for Oakleaf’s pre-acquisition period tax liabilities.
We maintain a liability for uncertain tax positions, the balance of which management believes is adequate.
Results of audit assessments by taxing authorities are not currently expected to have a material adverse impact on our results of operations or cash flows.12.
Restructuring The following table summarizes pre-tax restructuring charges, including employee severance and benefit costs and other charges, for the years ended December 31 for the respective periods (in millions):
## Table 3 ##
During the year ended December 31, 2013, we recognized a total of $18 million of pre-tax restructuring charges, of which $7 million was related to employee severance and benefit costs, including costs associated with our acquisitions of Greenstar and RCI and our 2012 restructurings discussed below.
The remaining charges were primarily related to operating lease obligations for property that will no longer be utilized.
We do not expect to incur any material charges associated with our past restructuring efforts in future periods.2012 Restructurings — In July 2012, we announced a reorganization of operations, designed to streamline management and staff support and reduce our cost structure, while not disrupting our front-line operations.
Principal organizational changes included removing the management layer of our four geographic Groups, each of which previously constituted a reportable segment, and consolidating and reducing the number of our geographic Areas through which we evaluate and oversee our Solid Waste subsidiaries from 22 to 17.
This reorganization eliminated approximately 700 employee positions throughout the Company, including positions at both the management and support level.
Voluntary separation arrangements were offered to many employees.
Additionally, in 2012, we recognized employee severance and benefits restructuring charges associated with the reorganization of Oakleaf discussed below that began in 2011 along with certain other actions taken by the Company in early 2012.

Tables referenced above, in order (Table 0 first):
<table><tr><td>Years ended December 31</td><td>2018</td><td>2017</td><td>2016</td></tr><tr><td>U.S.</td><td>$98</td><td>$105</td><td>$121</td></tr><tr><td>U.K.</td><td>45</td><td>43</td><td>43</td></tr><tr><td>Netherlands and Canada</td><td>25</td><td>25</td><td>27</td></tr><tr><td>Total</td><td>$168</td><td>$173</td><td>$191</td></tr></table>
<table><tr><td></td><td> 2013</td><td colspan="2">Period-to-Period Change</td><td> 2012</td><td colspan="2">Period-to-Period Change</td><td> 2011</td></tr><tr><td>Labor and related benefits</td><td>$2,506</td><td>$99</td><td>4.1%</td><td>$2,407</td><td>$71</td><td>3.0%</td><td>$2,336</td></tr><tr><td>Transfer and disposal costs</td><td>973</td><td>9</td><td>0.9</td><td>964</td><td>27</td><td>2.9</td><td>937</td></tr><tr><td>Maintenance and repairs</td><td>1,181</td><td>24</td><td>2.1</td><td>1,157</td><td>67</td><td>6.1</td><td>1,090</td></tr><tr><td>Subcontractor costs</td><td>1,182</td><td>-8</td><td>-0.7</td><td>1,190</td><td>242</td><td>25.5</td><td>948</td></tr><tr><td>Cost of goods sold</td><td>1,000</td><td>81</td><td>8.8</td><td>919</td><td>-152</td><td>-14.2</td><td>1,071</td></tr><tr><td>Fuel</td><td>603</td><td>-46</td><td>-7.1</td><td>649</td><td>21</td><td>3.3</td><td>628</td></tr><tr><td>Disposal and franchise fees and taxes</td><td>653</td><td>23</td><td>3.7</td><td>630</td><td>28</td><td>4.7</td><td>602</td></tr><tr><td>Landfill operating costs</td><td>232</td><td>8</td><td>3.6</td><td>224</td><td>-31</td><td>-12.2</td><td>255</td></tr><tr><td>Risk management</td><td>244</td><td>14</td><td>6.1</td><td>230</td><td>8</td><td>3.6</td><td>222</td></tr><tr><td>Other</td><td>538</td><td>29</td><td>5.7</td><td>509</td><td>57</td><td>12.6</td><td>452</td></tr><tr><td></td><td>$9,112</td><td>$233</td><td>2.6%</td><td>$8,879</td><td>$338</td><td>4.0%</td><td>$8,541</td></tr></table>
<table><tr><td></td><td> 2013</td><td colspan="2">Period-to- Period Change</td><td> 2012</td><td colspan="2">Period-to- Period Change</td><td> 2011</td></tr><tr><td>Depreciation of tangible property and equipment</td><td>$853</td><td>$20</td><td>2.4%</td><td>$833</td><td>$33</td><td>4.1%</td><td>$800</td></tr><tr><td>Amortization of landfill airspace</td><td>400</td><td>5</td><td>1.3</td><td>395</td><td>17</td><td>4.5</td><td>378</td></tr><tr><td>Amortization of intangible assets</td><td>80</td><td>11</td><td>15.9</td><td>69</td><td>18</td><td>35.3</td><td>51</td></tr><tr><td></td><td>$1,333</td><td>$36</td><td>2.8%</td><td>$1,297</td><td>$68</td><td>5.5%</td><td>$1,229</td></tr></table>
<table><tr><td></td><td> 2013</td><td> 2012</td><td> 2011</td></tr><tr><td>Solid Waste</td><td>$7</td><td>$19</td><td>$10</td></tr><tr><td>Wheelabrator</td><td>1</td><td>3</td><td>1</td></tr><tr><td>Corporate and Other</td><td>10</td><td>45</td><td>8</td></tr><tr><td></td><td>$18</td><td>$67</td><td>$19</td></tr></table>

Question: What's the average of the Solid Waste in the years where Amortization of landfill airspace is positive?
Answer: 12
Reasoning program: add(7,19), add(#0,10), divide(#1,3)