AMERICAN TOWER CORPORATION AND SUBSIDIARIES NOTES TO CONSOLIDATED FINANCIAL STATEMENTS—(Continued) 7.
DERIVATIVE FINANCIAL INSTRUMENTS Under the terms of the credit facility, the Company is required to enter into interest rate protection agreements on at least 50% of its variable rate debt.
Under these agreements, the Company is exposed to credit risk to the extent that a counterparty fails to meet the terms of a contract.
Such exposure is limited to the current value of the contract at the time the counterparty fails to perform.
The Company believes its contracts as of December 31, 2004 are with credit worthy institutions.
As of December 31, 2004, the Company had two interest rate caps outstanding with an aggregate notional amount of $350.0 million (each at an interest rate of 6.0%) that expire in 2006.
As of December 31, 2003, the Company had three interest rate caps outstanding with an aggregate notional amount of $500.0 million (each at a rate of 5.0%) that expired in 2004.
As of December 31, 2004 and 2003, there was no fair value associated with any of these interest rate caps.
During the year ended December 31, 2003, the Company recorded an unrealized loss of approximately $0.3 million (net of a tax benefit of approximately $0.2 million) in other comprehensive loss for the change in fair value of cash flow hedges and reclassified $5.9 million (net of a tax benefit of approximately $3.2 million) into results of operations.
During the year ended December 31, 2002, the Company recorded an unrealized loss of approximately $9.1 million (net of a tax benefit of approximately $4.9 million) in other comprehensive loss for the change in fair value of cash flow hedges and reclassified $19.5 million (net of a tax benefit of approximately $10.5 million) into results of operations.
Hedge ineffectiveness resulted in a gain of approximately $1.0 million for the year ended December 31, 2002, which is recorded in other expense in the accompanying consolidated statement of operations.
The Company records the changes in fair value of its derivative instruments that are not accounted for as hedges in other expense.
The Company did not reclassify any derivative losses into its statement of operations for the year ended December 31, 2004 and does not anticipate reclassifying any derivative losses into its statement of operations within the next twelve months, as there are no amounts included in other comprehensive loss as of December 31, 2004.8.
COMMITMENTS AND CONTINGENCIES Lease Obligations—The Company leases certain land, office and tower space under operating leases that expire over various terms.
Many of the leases contain renewal options with specified increases in lease payments upon exercise of the renewal option.
Escalation clauses present in operating leases, excluding those tied to CPI or other inflation-based indices, are straight-lined over the term of the lease.
(See note 1. )
Future minimum rental payments under non-cancelable operating leases include payments for certain renewal periods at the Company’s option because failure to renew could result in a loss of the applicable tower site and related revenues from tenant leases, thereby making it reasonably assured that the Company will renew the lease.
Such payments in effect at December 31, 2004 are as follows (in thousands):
## Table 0 ##
Aggregate rent expense (including the effect of straight-line rent expense) under operating leases for the years ended December 31, 2004, 2003 and 2002 approximated $118,741,000, $113,956,000, and $109,644,000, respectively.
Cost of revenue consists primarily of data center costs related to our co-located facilities, which include lease and hosting costs, related support and maintenance costs and energy and bandwidth costs, as well as depreciation of our servers and networking equipment, and personnel-related costs, including salaries, benefits and stock-based compensation, for our operations teams.
Cost of revenue also includes allocated facilities and other supporting overhead costs, amortization of acquired intangible assets and capitalized labor costs.
Many of the elements of our cost of revenue are relatively fixed, and cannot be reduced in the near term to offset any decline in our revenue.2014 Compared to 2013.
In 2014, cost of revenue increased by $179.6 million compared to 2013.
The increase was primarily attributable to a $75.5 million increase in depreciation expense related to additional server and networking equipment and amortization of acquired intangible assets, a $60.2 million increase in networking, hosting and data center costs related to our co-located facilities, a $27.0 million increase in allocated facilities and other supporting overhead costs due to the continued expansion of our real estate footprint and increase in support functions, and a $16.9 million increase in personnel-related costs, mainly driven by an increase in average employee headcount.2013 Compared to 2012.
In 2013, cost of revenue increased by $138.0 million compared to 2012.
The increase was primarily attributable to a $64.6 million increase in personnel-related costs, mainly driven by an increase in average employee headcount and recognition of stock-based compensation expense triggered by our initial public offering, a $34.4 million increase in depreciation expense related to capital leases for additional server and networking equipment, a $28.0 million increase in allocated facilities and other supporting overhead costs due to the continued expansion of our real estate footprint and increase in support functions, and a $14.8 million increase in data center costs related to our co-located facilities.
These increases were partially offset by a $3.8 million decrease in amortization of acquired intangible assets.
We plan to continue increasing the capacity and enhancing the capability and reliability of our infrastructure to support user growth and increased activity on our platform.
We expect that cost of revenue 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.
Research and Development
## Table 1 ##
Research and development expenses consist primarily of personnel-related costs, including salaries, benefits and stock-based compensation, for our engineers and other employees engaged in the research and development of our products and services.
In addition, research and development expenses include amortization of acquired intangible assets, allocated facilities and other supporting overhead costs.2014 Compared to 2013.
In 2014, research and development expenses increased by $97.6 million compared to 2013.
The increase was primarily attributable to a $107.2 million increase in personnel-related costs, mainly driven by an increase in average employee headcount, and a $34.3 million increase in allocated facilities and other supporting overhead expenses due to the continued expansion of our real estate footprint and increase in support functions.
These increases were partially offset by a $43.9 million increase in the capitalization of costs associated with developing software for internal use.2013 Compared to 2012.
In 2013, research and development expenses increased by $475.0 million compared to 2012.
The increase was primarily attributable to a $466.7 million increase in personnel-related costs, mainly driven by an increase in average employee headcount and recognition of stock-based compensation expense triggered by our initial public offering, and a $32.3 million increase in allocated facilities and other supporting overhead expenses due to the continued expansion of our real estate footprint and increase in support functions.
These increases were partially offset by a $24.0 million increase in the capitalization of costs associated with developing software for internal use.
We plan to continue to hire employees for our engineering, product management and design teams to support our research and development efforts.
We expect that research and development costs 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.
(1) Costs and expenses include stock-based compensation expense as follows:
## Table 2 ##
(2) The following table presents a reconciliation of net loss to Adjusted EBITDA for each of the periods indicated:
## Table 3 ##
(3) The following table presents a reconciliation of net loss to non-GAAP net income (loss) for each of the periods indicated:
## Table 4 ##
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 45%, 43% and 35% between the third and fourth quarters of 2012, 2013 and 2014, respectively, while advertising revenue for the first quarter of 2013 and 2014 increased 1% and 3% compared to the fourth quarter of 2012 and 2013, respectively.
Cost of Revenue and Operating Expenses Cost of revenue, excluding the impact of stock-based compensation expense, increased in every quarter presented primarily due to the continued expansion of our co-located data center facilities and an increase in average employee headcount.
Legal Proceedings The Company is currently involved in, and may in the future be involved in, legal proceedings, claims and governmental investigations in the normal course of business.
Legal fees and other costs associated with such actions are expensed as incurred.
The Company assesses, in conjunction with its legal counsel, the need to record a liability for litigation and contingencies.
Litigation accruals are recorded when and if it is determined that a loss related matter is both probable and reasonably estimable.
Material loss contingencies that are reasonably possible of occurrence, if any, are subject to disclosure.
As of December 31, 2014, there was no litigation or contingency with at least a reasonable possibility of a material loss.
No material losses have been recorded during years ended December 31, 2014, 2013 and 2012 with respect to litigation or loss contingencies.
Indemnification In the ordinary course of business, the Company often includes standard indemnification provisions in its arrangements with its customers, partners, suppliers and vendors.
Pursuant to these provisions, the Company may be obligated to indemnify such parties for losses or claims suffered or incurred in connection with its service, breach of representations or covenants, intellectual property infringement or other claims made against such parties.
These provisions may limit the time within which an indemnification claim can be made.
It is not possible to determine the maximum potential amount under these indemnification obligations due to the limited history of prior indemnification claims and the unique facts and circumstances involved in each particular agreement.
The Company has never incurred significant expense defending its licensees against third party claims, nor has it ever incurred significant expense under its standard service warranties or arrangements with its customers, partners, suppliers and vendors.
Accordingly, the Company had no liabilities recorded for these provisions as of December 31, 2014 and 2013.
Note 15.
Related Party Transactions One of the Company’s directors has a direct ownership interest in a vendor that provides marketing and communication services to the Company.
For the years ended December 31, 2014 and 2013, no expenses were incurred for services rendered.
For the year ended December 31, 2012, the Company incurred $1.9 million of expense for services rendered.
There was no outstanding payable balance associated with the vendor as of December 31, 2014.
Note 16.
Employee Benefit Plan The Company adopted a 401(k) Plan that qualifies as a deferred compensation arrangement under Section 401 of the Code.
Under the 401(k) Plan, participating employees may defer a portion of their pretax earnings not to exceed the maximum amount allowable.
The Company has not made any matching contributions to date.
Note 17.
Segment Information and Operations by Geographic Area The Company has a single operating segment and reporting unit structure.
The Company’s chief operating decisionmaker is the chief executive officer who reviews financial information presented on a consolidated basis, accompanied by disaggregated information about revenue by geographic region for purposes of allocating resources and evaluating financial performance.
Revenue Revenue by geography is based on the billing addresses of the customers.
The following tables set forth revenue by services and revenue by geographic area (in thousands):

<table><tr><td>2005</td><td>$106,116</td></tr><tr><td>2006</td><td>106,319</td></tr><tr><td>2007</td><td>106,095</td></tr><tr><td>2008</td><td>106,191</td></tr><tr><td>2009</td><td>106,214</td></tr><tr><td>Thereafter</td><td>1,570,111</td></tr><tr><td>Total</td><td>$2,101,046</td></tr></table>
<table><tr><td></td><td colspan="3">Year Ended December 31,</td><td rowspan="2">2013 to 2014 % Change</td><td rowspan="2">2012 to 2013 % Change</td></tr><tr><td></td><td>2014</td><td>2013</td><td>2012</td></tr><tr><td></td><td colspan="3">(in thousands)</td><td></td><td></td></tr><tr><td>Research and development</td><td>$691,543</td><td>$593,992</td><td>$119,004</td><td>16%</td><td>399%</td></tr><tr><td>Research and development as a percentage of revenue</td><td>49%</td><td>89%</td><td>38%</td><td></td><td></td></tr></table>
<table><tr><td></td><td colspan="8">Three Months Ended</td></tr><tr><td></td><td>Dec. 31, 2014</td><td>Sep. 30, 2014</td><td>Jun. 30, 2014</td><td>Mar. 31, 2014</td><td>Dec. 31, 2013</td><td>Sep. 30, 2013</td><td>Jun. 30, 2013</td><td>Mar. 31, 2013</td></tr><tr><td></td><td colspan="8">(Unaudited, in thousands)</td></tr><tr><td>Cost of revenue</td><td>$13,240</td><td>$13,596</td><td>$13,869</td><td>$9,831</td><td>$45,927</td><td>$3,060</td><td>$1,471</td><td>$484</td></tr><tr><td>Research and development</td><td>95,942</td><td>93,973</td><td>92,493</td><td>78,318</td><td>326,536</td><td>29,180</td><td>15,772</td><td>8,425</td></tr><tr><td>Sales and marketing</td><td>49,031</td><td>42,884</td><td>37,547</td><td>27,801</td><td>104,084</td><td>5,742</td><td>2,549</td><td>2,065</td></tr><tr><td>General and administrative</td><td>19,002</td><td>19,149</td><td>14,502</td><td>10,419</td><td>44,650</td><td>5,620</td><td>2,854</td><td>1,948</td></tr><tr><td>Total stock-based compensation expense</td><td>$177,215</td><td>$169,602</td><td>$158,411</td><td>$126,369</td><td>$521,197</td><td>$43,602</td><td>$22,646</td><td>$12,922</td></tr></table>
<table><tr><td></td><td colspan="8">Three Months Ended</td></tr><tr><td></td><td>Dec. 31, 2014</td><td>Sep. 30, 2014</td><td>Jun. 30, 2014</td><td>Mar. 31, 2014</td><td>Dec. 31, 2013</td><td>Sep. 30, 2013</td><td>Jun. 30, 2013</td><td>Mar. 31, 2013</td></tr><tr><td></td><td colspan="8">(Unaudited, in thousands)</td></tr><tr><td>Reconciliation of Net Loss to Adjusted EBITDA:</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Net loss</td><td>$-125,352</td><td>$-175,464</td><td>$-144,642</td><td>$-132,362</td><td>$-511,471</td><td>$-64,601</td><td>$-42,225</td><td>$-27,026</td></tr><tr><td>Stock-based compensation expense</td><td>177,215</td><td>169,602</td><td>158,411</td><td>126,369</td><td>521,197</td><td>43,602</td><td>22,646</td><td>12,922</td></tr><tr><td>Depreciation and amortization expense</td><td>62,428</td><td>60,155</td><td>45,631</td><td>39,951</td><td>33,224</td><td>29,023</td><td>25,917</td><td>22,730</td></tr><tr><td>Interest and other expense (income)</td><td>23,512</td><td>13,874</td><td>330</td><td>1,769</td><td>5,112</td><td>909</td><td>2,532</td><td>2,762</td></tr><tr><td>Provision (benefit) for income taxes</td><td>3,687</td><td>159</td><td>-5,599</td><td>1,222</td><td>-3,317</td><td>360</td><td>777</td><td>357</td></tr><tr><td>Adjusted EBITDA</td><td>$141,490</td><td>$68,326</td><td>$54,131</td><td>$36,949</td><td>$44,745</td><td>$9,293</td><td>$9,647</td><td>$11,745</td></tr></table>
<table><tr><td></td><td colspan="8">Three Months Ended</td></tr><tr><td></td><td>Dec. 31, 2014</td><td>Sep. 30, 2014</td><td>Jun. 30, 2014</td><td>Mar. 31, 2014</td><td>Dec. 31, 2013</td><td>Sep. 30, 2013</td><td>Jun. 30, 2013</td><td>Mar. 31, 2013</td></tr><tr><td></td><td colspan="8">(Unaudited, in thousands)</td></tr><tr><td>Reconciliation of Net Loss to Non-GAAP Net Income (Loss):</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Net loss</td><td>$-125,352</td><td>$-175,464</td><td>$-144,642</td><td>$-132,362</td><td>$-511,471</td><td>$-64,601</td><td>$-42,225</td><td>$-27,026</td></tr><tr><td>Stock-based compensation expense</td><td>177,215</td><td>169,602</td><td>158,411</td><td>126,369</td><td>521,197</td><td>43,602</td><td>22,646</td><td>12,922</td></tr><tr><td>Amortization of acquired intangible assets</td><td>10,419</td><td>11,869</td><td>8,099</td><td>6,176</td><td>5,569</td><td>3,783</td><td>3,302</td><td>3,876</td></tr><tr><td>Non-cash interest expense related to convertible notes</td><td>16,412</td><td>2,411</td><td>—</td><td>—</td><td>—</td><td>—</td><td>—</td><td>—</td></tr><tr><td>Income tax effects related to acquisitions</td><td>626</td><td>-1,446</td><td>-7,272</td><td>—</td><td>-5,521</td><td>—</td><td>-87</td><td>-296</td></tr><tr><td>Non-GAAP net income (loss)</td><td>$79,320</td><td>$6,972</td><td>$14,596</td><td>$183</td><td>$9,774</td><td>$-17,216</td><td>$-16,364</td><td>$-10,524</td></tr></table>

Question: Which element exceeds 90 % of total for Mar. 31, 2014?
Answer: Stock-based compensation expense, Depreciation and amortization expense