adequacy of our provision for income taxes, we regularly assess the likelihood of adverse outcomes resulting from tax examinations.
While it is often difficult to predict the final outcome or the timing of the resolution of a tax examination, our reserves for uncertain tax benefits reflect the outcome of tax positions that are more likely than not to occur.
While we believe that we have complied with all applicable tax laws, there can be no assurance that a taxing authority will not have a different interpretation of the law and assess us with additional taxes.
Should additional taxes be assessed, this may result in a material adverse effect on our results of operations and financial condition.
ITEM 1B.
UNRESOLVED STAFF COMMENTS We have no unresolved SEC staff comments to report.
ITEM 2.
PROPERTIES As of December 31, 2018, we owned or leased 126 major manufacturing sites and 15 major technical centers.
A manufacturing site may include multiple plants and may be wholly or partially owned or leased.
We also have many smaller manufacturing sites, sales offices, warehouses, engineering centers, joint ventures and other investments strategically located throughout the world.
We have a presence in 44 countries.
The following table shows the regional distribution of our major manufacturing sites by the operating segment that uses such facilities:
## Table 0 ##
In addition to these manufacturing sites, we had 15 major technical centers: eight in North America; two in Europe, Middle East and Africa; and five in Asia Pacific.
Of our 126 major manufacturing sites and 15 major technical centers, which include facilities owned or leased by our consolidated subsidiaries, 61 are primarily owned and 80 are primarily leased.
We frequently review our real estate portfolio and develop footprint strategies to support our customers’ global plans, while at the same time supporting our technical needs and controlling operating expenses.
We believe our evolving portfolio will meet current and anticipated future needs.
ITEM 3.
LEGAL PROCEEDINGS We are from time to time subject to various actions, claims, suits, government investigations, and other proceedings incidental to our business, including those arising out of alleged defects, breach of contracts, competition and antitrust matters, product warranties, intellectual property matters, personal injury claims and employment-related matters.
It is our opinion that the outcome of such matters will not have a material adverse impact on our consolidated financial position, results of operations, or cash flows.
With respect to warranty matters, although we cannot ensure that the future costs of warranty claims by customers will not be material, we believe our established reserves are adequate to cover potential warranty settlements.
However, the final amounts required to resolve these matters could differ materially from our recorded estimates.
Brazil Matters Aptiv conducts business operations in Brazil that are subject to the Brazilian federal labor, social security, environmental, tax and customs laws, as well as a variety of state and local laws.
While Aptiv believes it complies with such laws, they are complex, subject to varying interpretations, and the Company is often engaged in litigation with government agencies regarding the application of these laws to particular circumstances.
As of December 31, 2018, the majority of claims asserted against Aptiv in Brazil relate to such litigation.
The remaining claims in Brazil relate to commercial and labor litigation with private parties.
As of December 31, 2018, claims totaling approximately $145 million (using December 31, 2018 foreign currency rates) have been asserted against Aptiv in Brazil.
As of December 31, 2018, the Company maintains accruals for these asserted claims of $30 million (using December 31, 2018 foreign currency rates).
The amounts accrued represent claims that are deemed probable of loss and are reasonably estimable based on the Company’s analyses and assessment of the asserted claims and prior experience with similar matters.
While the Company believes its accruals are adequate, the final amounts required to resolve these matters could differ materially from the Company’s recorded estimates and Aptiv’s results of
General and Administrative General and administrative expenses consist primarily of personnel-related costs, including salaries, benefits and stock-based compensation, for our executive, finance, legal, information technology, human resources and other administrative employees.
In addition, general and administrative expenses include fees and costs for professional services, including consulting, third-party legal and accounting services and facilities and other supporting overhead costs that are not allocated to other departments.
## Table 1 ##
2015 Compared to 2014.
In 2015, general and administrative expense increased by $70.8 million compared to 2014.
The increase was primarily attributable to a $63.7 million increase in personnel-related costs, mainly driven by an increase in average employee headcount, increase in compensation and recognition of stock-based compensation expense, an increase of $11.0 million in fees and costs for professional services, offset by a $3.9 million decrease in unallocated facilities and supporting costs.2014 Compared to 2013.
In 2014, general and administrative expense increased by $66.1 million compared to 2013.
The increase was primarily attributable to a $51.3 million increase in personnel-related costs, mainly driven by an increase in average employee headcount and recognition of stock-based compensation expense, an increase of $16.3 million in fees and costs for professional services, partially offset by a $1.5 million decrease in unallocated facilities and supporting costs, driven by slower headcount growth in the general and administrative function relative to other functional areas.
We plan to continue to expand our business both domestically and internationally, and expect to increase the size of our general and administrative function to help grow our business.
We expect that general and administrative expenses will increase in absolute dollar amounts for the foreseeable future and vary in the near term from period to period as a percentage of revenue.
Interest Expense Interest expense consists primarily of interest expense incurred in connection with the $935.0 million principal amount of 0.25% convertible senior notes due 2019, or the 2019 Notes, and $954.0 million principal amount of 1.00% convertible senior notes due 2021, or the 2021 Notes and together with the 2019 Notes, the Notes, and interest expense related to capital leases and other financing facilities.
## Table 2 ##
2015 Compared to 2014.
In 2015, interest expense increased by $62.3 million compared to 2014.
The increase was primarily attributable to a full year of interest expense related to the amortization of the debt discount and accrued coupon interest expense of the Notes as compared to a partial year of interest expense recorded in 2014, as the Notes were issued in the third quarter of 2014.
Interest expense in 2015 was comprised of $89.4 million of total interest expense related to the Notes as well as the credit facility and $8.8 million related to capital leases of equipment.2014 Compared to 2013.
In 2014, interest expense increased by $28.3 million compared to 2013.
The increase was primarily attributable to the interest expense related to the amortization of the debt discount and accrued coupon interest expense of the Notes, which were issued in 2014.
Interest expense in 2014 was comprised of $25.7 million of interest expense related to the Notes and the credit facility and $10.2 million related to capital leases of equipment.
Historically, we incurred interest expense primarily from capital leases of equipment.
(1) Costs and expenses include stock-based compensation expense as follows:
## Table 3 ##
(2) The following table presents a reconciliation of net loss to Adjusted EBITDA for each of the periods indicated:
## Table 4 ##
(3) The following table presents a reconciliation of net loss to non-GAAP net income for each of the periods indicated:
## Table 5 ##
Quarterly Trends Revenue Spending by advertisers is traditionally strongest in the fourth quarter of each year.
Historically, this seasonality in advertising spending has affected our quarterly results with higher sequential advertising revenue growth from the third to the fourth quarter compared to sequential advertising revenue growth from the fourth quarter to the subsequent first quarter.
For example, our advertising revenue increased 43%, 35% and 25% between the third and fourth quarters of 2013, 2014 and 2015, respectively, while advertising revenue for the first quarter of 2014 and 2015 increased 3% and decreased 10% compared to the fourth quarter of 2013 and 2014, respectively.
Total Costs and Expenses Total costs and expenses, which include significant amounts of stock-based compensation expense, increased in every quarter presented primarily due to the continued expansion of our facilities and an increase in average employee headcount.
The increase in total costs and expenses in the fourth quarter of 2015 was the result of an increase in advertising costs as well as an increase in traffic acquisition costs as a result of the growth of sale to advertisers of our advertising products which we place on third-party publishers’ websites, applications or other offerings.
Credit Facility In October 2013, we entered into a revolving credit agreement with certain lenders which provides for a $1.0 billion revolving unsecured credit facility maturing on October 22, 2018.
Loans under the credit facility bear interest, at our option, at (i) a base rate based on the highest of the prime rate, the federal funds rate plus 0.50% and an adjusted LIBOR rate for a one-month interest period plus 1.00%, in each case plus a margin ranging from 0.00% to 0.75% or (ii) an adjusted LIBOR rate plus a margin ranging from 1.00% to 1.75%.
This margin is determined based on our total leverage ratio for the preceding four fiscal quarter period.
We are also obligated to pay other customary fees for a credit facility of this size and type, including an upfront fee and an unused commitment fee.
Our obligations under the credit facility are guaranteed by one of our wholly-owned subsidiaries.
In addition, the credit facility contains restrictions on payments including cash payment of dividends.
The revolving credit agreement was amended in September 2014 to increase the amount of indebtedness that we may incur and increase the amount of restricted payments that we may make.
This amendment to the revolving credit agreement also provides that if our total leverage ratio exceeds 2.5:1.0 and if the amount outstanding under the credit facility exceeds $500.0 million, or 50% of the amount that may be borrowed under the credit facility, the credit facility will become secured by substantially all of our and certain of our subsidiaries’ assets, subject to limited exceptions.
As of December 31, 2015, no amounts were drawn under the credit facility.
Liquidity and Capital Resources

<table><tr><td></td><td>North America</td><td>Europe,Middle East& Africa</td><td>Asia Pacific</td><td>South America</td><td>Total</td></tr><tr><td>Signal and Power Solutions</td><td>45</td><td>33</td><td>33</td><td>5</td><td>116</td></tr><tr><td>Advanced Safety and User Experience</td><td>2</td><td>5</td><td>3</td><td>—</td><td>10</td></tr><tr><td>Total</td><td>47</td><td>38</td><td>36</td><td>5</td><td>126</td></tr></table>
<table><tr><td></td><td colspan="3">Year Ended December 31,</td><td rowspan="2">2014 to 2015 % Change</td><td rowspan="2">2013 to 2014 % Change</td></tr><tr><td></td><td>2015</td><td>2014</td><td>2013</td></tr><tr><td></td><td colspan="3">(in thousands)</td><td></td><td></td></tr><tr><td>General and administrative</td><td>$260,673</td><td>$189,906</td><td>$123,795</td><td>37%</td><td>53%</td></tr><tr><td>General and administrative as a percentage of revenue</td><td>12%</td><td>14%</td><td>19%</td><td></td><td></td></tr></table>
<table><tr><td></td><td colspan="3">Year Ended December 31,</td></tr><tr><td></td><td>2015</td><td>2014</td><td>2013</td></tr><tr><td></td><td colspan="3">(In thousands)</td></tr><tr><td>Interest expense</td><td>$98,178</td><td>$35,918</td><td>$7,576</td></tr></table>
<table><tr><td></td><td colspan="8">Three Months Ended</td></tr><tr><td></td><td>Dec. 31, 2015</td><td>Sep. 30, 2015</td><td>Jun. 30, 2015</td><td>Mar. 31, 2015</td><td>Dec. 31, 2014</td><td>Sep. 30, 2014</td><td>Jun. 30, 2014</td><td>Mar. 31, 2014</td></tr><tr><td></td><td colspan="8">(Unaudited, in thousands)</td></tr><tr><td>Cost of revenue</td><td>$8,360</td><td>$8,973</td><td>$10,486</td><td>$12,886</td><td>$13,240</td><td>$13,596</td><td>$13,869</td><td>$9,831</td></tr><tr><td>Research and development</td><td>94,707</td><td>100,673</td><td>103,121</td><td>103,036</td><td>95,942</td><td>93,973</td><td>92,493</td><td>78,318</td></tr><tr><td>Sales and marketing</td><td>36,750</td><td>37,889</td><td>39,607</td><td>42,658</td><td>49,031</td><td>42,884</td><td>37,547</td><td>27,801</td></tr><tr><td>General and administrative</td><td>18,432</td><td>18,386</td><td>21,929</td><td>24,225</td><td>19,002</td><td>19,149</td><td>14,502</td><td>10,419</td></tr><tr><td>Total stock-based compensation expense</td><td>$158,249</td><td>$165,921</td><td>$175,143</td><td>$182,805</td><td>$177,215</td><td>$169,602</td><td>$158,411</td><td>$126,369</td></tr></table>
<table><tr><td></td><td colspan="8">Three Months Ended</td></tr><tr><td></td><td>Dec. 31, 2015</td><td>Sep. 30, 2015</td><td>Jun. 30, 2015</td><td>Mar. 31, 2015</td><td>Dec. 31, 2014</td><td>Sep. 30, 2014</td><td>Jun. 30, 2014</td><td>Mar. 31, 2014</td></tr><tr><td></td><td colspan="8">(Unaudited, in thousands)</td></tr><tr><td>Reconciliation of Net Loss to Adjusted EBITDA:</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Net loss</td><td>$-90,236</td><td>$-131,690</td><td>$-136,663</td><td>$-162,442</td><td>$-125,352</td><td>$-175,464</td><td>$-144,642</td><td>$-132,362</td></tr><tr><td>Stock-based compensation expense</td><td>158,249</td><td>165,921</td><td>175,143</td><td>182,805</td><td>177,215</td><td>169,602</td><td>158,411</td><td>126,369</td></tr><tr><td>Depreciation and amortization expense</td><td>87,446</td><td>81,464</td><td>76,049</td><td>67,864</td><td>62,428</td><td>60,155</td><td>45,631</td><td>39,951</td></tr><tr><td>Interest and other expense (income)</td><td>19,652</td><td>23,291</td><td>25,132</td><td>15,194</td><td>23,512</td><td>13,874</td><td>330</td><td>1,769</td></tr><tr><td>Provision (benefit) for income taxes</td><td>3,405</td><td>3,162</td><td>-19,473</td><td>632</td><td>3,687</td><td>159</td><td>-5,599</td><td>1,222</td></tr><tr><td>Restructuring charges</td><td>12,902</td><td>—</td><td>—</td><td>—</td><td>—</td><td>—</td><td>—</td><td>—</td></tr><tr><td>Adjusted EBITDA</td><td>$191,418</td><td>$142,148</td><td>$120,188</td><td>$104,053</td><td>$141,490</td><td>$68,326</td><td>$54,131</td><td>$36,949</td></tr></table>
<table><tr><td></td><td colspan="8">Three Months Ended</td></tr><tr><td></td><td>Dec. 31, 2015</td><td>Sep. 30, 2015</td><td>Jun. 30, 2015</td><td>Mar. 31, 2015</td><td>Dec. 31, 2014</td><td>Sep. 30, 2014</td><td>Jun. 30, 2014</td><td>Mar. 31, 2014</td></tr><tr><td></td><td colspan="8">(Unaudited, in thousands)</td></tr><tr><td>Reconciliation of Net Loss to Non-GAAP Net Income:</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Net loss</td><td>$-90,236</td><td>$-131,690</td><td>$-136,663</td><td>$-162,442</td><td>$-125,352</td><td>$-175,464</td><td>$-144,642</td><td>$-132,362</td></tr><tr><td>Stock-based compensation expense</td><td>158,249</td><td>165,921</td><td>175,143</td><td>182,805</td><td>177,215</td><td>169,602</td><td>158,411</td><td>126,369</td></tr><tr><td>Amortization of acquired intangible assets</td><td>15,418</td><td>14,481</td><td>13,965</td><td>10,795</td><td>10,419</td><td>11,869</td><td>8,099</td><td>6,176</td></tr><tr><td>Non-cash interest expense related to convertible notes</td><td>18,046</td><td>17,495</td><td>17,006</td><td>16,638</td><td>16,412</td><td>2,411</td><td>—</td><td>—</td></tr><tr><td>Non-cash expense related to acquisitions</td><td>—</td><td>—</td><td>926</td><td>—</td><td>—</td><td>—</td><td>—</td><td>—</td></tr><tr><td>Income tax effects related to acquisitions</td><td>240</td><td>777</td><td>-21,859</td><td>-1,288</td><td>626</td><td>-1,446</td><td>-7,272</td><td>—</td></tr><tr><td>Restructuring charges</td><td>12,902</td><td>—</td><td>—</td><td>—</td><td>—</td><td>—</td><td>—</td><td>—</td></tr><tr><td>Non-GAAP net income</td><td>$114,619</td><td>$66,984</td><td>$48,518</td><td>$46,508</td><td>$79,320</td><td>$6,972</td><td>$14,596</td><td>$183</td></tr></table>

Question: Which year is Depreciation and amortization expense the highest?
Answer: Dec. 31, 2015