Notes to Consolidated Financial Statements (continued) March 31, 2003 (I) Intellectual Property The Company capitalizes as intellectual property costs incurred, excluding costs associated with Company personnel, relating to patenting its technology.
Capitalized costs, the majority of which represent legal costs, reflect the cost of both awarded patents and patents pending.
The Company amortizes the cost of these patents on a straight-line basis over a period of seven years.
If the Company elects to stop pursuing a particular patent application or determines that a patent application is not likely to be awarded for a particular patent or elects to discontinue payment of required maintenance fees for a particular patent, the Company at that time records as expense the net capitalized amount of such patent application or patent.
The Company does not capitalize maintenance fees for patents.
(J) Net Loss per Share Basic net loss per share is computed by dividing net loss by the weighted-average number of common shares outstanding during the fiscal year.
Diluted net loss per share is computed by dividing net loss by the weighted-average number of dilutive common shares outstanding during the fiscal year.
Diluted weighted-average shares reflect the dilutive effect, if any, of potential common stock such as options and warrants based on the treasury stock method.
No potential common stock is considered dilutive in periods in which a loss is reported, such as the fiscal years ended March 31, 2001, 2002 and 2003, because all such common equivalent shares would be antidilutive.
The calculation of diluted weighted-average shares outstanding for the years ended March 31, 2001, 2002 and 2003 excludes the options to purchase common stock as shown below.
## Table 0 ##
The calculation of diluted weighted-average shares outstanding excludes unissued shares of Common Stock associated with outstanding stock options that have exercise prices greater than the average market price of ABIOMED Common Stock during the period.
For the fiscal years ending March 31, 2001, 2002 and 2003, the weighted-average number of these potential shares totaled 61,661, 341,495 and 2,463,715 shares, respectively.
The calculation of diluted weighted-average shares outstanding for the years ended March 31, 2001, 2002 and 2003 also excludes warrants to purchase 400,000 shares of common stock issued in connection with the acquisition of intellectual property (see Note 4).
(K) Cash and Cash Equivalents The Company classifies any marketable security with a maturity date of 90 days or less at the time of purchase as a cash equivalent.
(L) Marketable Securities The Company classifies any security with a maturity date of greater than 90 days at the time of purchase as marketable securities and classifies marketable securities with a maturity date of greater than one year from the balance sheet date as long-term investments.
Under Statement of Financial Accounting Standards (SFAS) No.115, Accounting for Certain Investments in Debt and Equity Securities, securities that the Company has the positive intent and ability to hold to maturity are reported at amortized cost and classified as held-to-maturity securities.
The amortized cost and market value of marketable securities were approximately $25,654,000 and $25,661,000 at March 31, 2002, and $9,877,000 and $9,858,000 at March 31, 2003, respectively.
At March 31, 2003, these short-term investments consisted primarily of government securities.
(M) Disclosures about Fair Value of Financial Instruments As of March 31, 2002 and 2003, the Company’s financial instruments were comprised of cash and cash equivalents, marketable securities, accounts receivable and accounts payable, the carrying amounts of which approximated fair market value.
(N) Comprehensive Income SFAS No.130, Reporting Comprehensive Income, requires disclosure of all components of comprehensive income and loss on an annual and interim basis.
Comprehensive income and loss is defined as the change in equity of a business enterprise during a period from transactions and other events and circumstances from non-owner sources.
Other than the reported net loss, there were no components of comprehensive income or loss which require disclosure for the years ended March 31, 2001, 2002 and 2003.
Note G – Environmental Matters Superfund Sites Hazardous substances, such as asbestos, polychlorinated biphenyls (PCBs) and coal tar, have been used or generated in the course of operations of the Utilities and their predecessors and are present at sites and in facilities and equipment they currently or previously owned, including sites at which gas was manufactured or stored.
The Federal Comprehensive Environmental Response, Compensation and Liability Act of 1980 and similar state statutes (Superfund) impose joint and several liability, regardless of fault, upon generators of hazardous substances for investigation and remediation costs (which includes costs of demolition, removal, disposal, storage, replacement, containment and monitoring) and environmental damages.
Liability under these laws can be material and may be imposed for contamination from past acts, even though such past acts may have been lawful at the time they occurred.
The sites at which the Utilities have been asserted to have liability under these laws, including their manufactured gas sites, are referred to herein as “Superfund Sites.
” For Superfund Sites where there are other potentially responsible parties and the Utilities are not managing the site investigation and remediation, the accrued liability represents an estimate of the amount the Utilities will need to pay to discharge their related obligations.
For Superfund Sites (including the manufactured gas sites) for which one of the Utilities is managing the investigation and remediation, the accrued liability represents an estimate of the undiscounted cost to investigate the sites and, for sites that have been investigated in whole or in part, the cost to remediate the sites in light of the information available, applicable remediation standards and experience with similar sites.
For the 12 months ended December 31, 2003, Con Edison of New York and O&R incurred approximately $21 million and $5 million, respectively, for environmental remediation costs.
No insurance recoveries were received.
For the 12 months ended December 31, 2002, Con Edison of New York and O&R incurred approximately $22 million and $2 million, respectively, for environmental remediation costs, and O&R received insurance recoveries of $7 million.
The accrued liabilities and regulatory assets related to Superfund Sites for each of the Companies at December 31, 2003 and December 31, 2002 were as follows:
## Table 1 ##
Most of the accrued Superfund Site liability relates to Superfund Sites that have been investigated, in whole or in part.
As investigations progress on these and other sites, the Companies expect that additional liability will be accrued, the amount of which is not presently determinable but may be material.
The Utilities are permitted under their current rate agreements to recover or defer as regulatory assets (for subsequent recovery through rates) certain site investigation and remediation costs.
Con Edison of New York estimated in 2002 that for its manufactured gas sites, many of which have not been investigated, its aggregate undiscounted potential liability for the investigation and remediation of coal tar and/or other manufactured gas plant-related environmental contaminants could range from approximately $65 million to $1.1 billion.
O&R estimated in 2002 that for its manufactured gas sites the aggregate undiscounted potential liability for the remediation of such contaminants could range from approximately $25 million to $95 million.
These estimates were based on the assumption that there is contamination at each of the sites and additional assumptions regarding the extent of contamination and the type and extent of remediation that may be required.
Actual experience may be materially different.
Asbestos Proceedings Suits have been brought in New York State and federal courts against the Utilities and many other defendants, wherein a large number of plaintiffs sought large amounts of compensatory and punitive damages for deaths and injuries allegedly caused by exposure to asbestos at various premises of the Utilities.
The suits that have been resolved, which are many, have been resolved without any payment by the Utilities, or for amounts that were not, in the aggregate, material to them.
The amounts specified in all the remaining thousands of suits total billions of dollars but the Companies believe that these amounts are greatly exaggerated, as experienced through the disposition of previous claims.
Con Edison of New York estimated in 2002 that its aggregate undiscounted potential liability for these suits and additional such suits that may be brought over the next 50 years ranges from approximately $38 million to $162 million (with no amount within the range considered
Notes to the Financial Statements — Continued Asbestos Proceedings Suits have been brought in New York State and federal courts against the Utilities and many other defendants, wherein a large number of plaintiffs sought large amounts of compensatory and punitive damages for deaths and injuries allegedly caused by exposure to asbestos at various premises of the Utilities.
The suits that have been resolved, which are many, have been resolved without any payment by the Utilities, or for amounts that were not, in the aggregate, material to them.
The amounts specified in all the remaining thousands of suits total billions of dollars; however, the Utilities believe that these amounts are greatly exaggerated, based on the disposition of previous claims.
In 2010, CECONY estimated that its aggregate undiscounted potential liability for these suits and additional suits that may be brought over the next 15 years is $10 million.
The estimate was based upon a combination of modeling, historical data analysis and risk factor assessment.
Actual experience may be materially different.
In addition, certain current and former employees have claimed or are claiming workers’ compensation benefits based on alleged disability from exposure to asbestos.
Under its current rate agreements, CECONY is permitted to defer as regulatory assets (for subsequent recovery through rates) costs incurred for its asbestos lawsuits and workers’ compensation claims.
The accrued liability for asbestos suits and workers’ compensation proceedings (including those related to asbestos exposure) and the amounts deferred as regulatory assets for the Companies at December 31, 2010 and 2009 were as follows:
## Table 2 ##
Note H — Other Material Contingencies Manhattan Steam Main Rupture In July 2007, a CECONY steam main located in midtown Manhattan ruptured.
It has been reported that one person died and others were injured as a result of the incident.
Several buildings in the area were damaged.
Debris from the incident included dirt and mud containing asbestos.
The response to the incident required the closing of several buildings and streets for various periods.
Approximately 110 suits are pending against the company seeking generally unspecified compensatory and, in some cases, punitive damages, for personal injury, property damage and business interruption.
The company has not accrued a liability for the suits.
The company has notified its insurers of the incident and believes that the policies in force at the time of the incident will cover most of the company’s costs, which the company is unable to estimate, but which could be substantial, to satisfy its liability to others in connection with the incident.
Investigations of Vendor Payments In January 2009, CECONY commenced an internal investigation relating to the arrests of certain employees and retired employees (all of whom have since pleaded guilty) for accepting kickbacks from contractors that performed construction work for the company.
The company has retained a law firm, which has retained an accounting firm, to assist in the company’s investigation.
The company is providing information to governmental authorities, which consider the company to be a victim of unlawful conduct, in connection with their investigation of the arrested employees and contractors.
The company has terminated its employment of the arrested employees and its contracts with the contractors (one of which is suing the company for substantial damages claiming wrongful termination).
In February 2009, the NYSPSC commenced a proceeding that, among other things, will examine the prudence of certain of the company’s expenditures relating to the arrests and consider whether additional expenditures should also be examined (see “Other Regulatory Matters” in Note B).
CECONY is also investigating the September 2010 arrest of a retired employee (for participating in a bribery scheme in which the employee received payments from a bidder that was selected to supply materials to the company) and the January 2011 arrest of an employee (for accepting kickbacks from an engineering firm that performed work for the company).
CECONY has provided information to governmental authorities in connection with their ongoing investigations of these matters.
The company, based upon its evaluation of its internal controls for 2010 and previous years, believes that the controls were effective to provide reasonable assurance that its financial statements have been fairly presented, in all material respects, in conformity with generally accepted accounting principles.
Because the company’s investigations are ongoing, the company is unable to predict the impact of any of the employees’ unlawful conduct on the company’s internal controls, business, results of operations or financial position.
Other Contingencies See “Lease In/Lease Out Transactions” in Note J.
Guarantees Con Edison and its subsidiaries enter into various agreements providing financial or performance assurance primarily to third parties on behalf of their subsidiaries.
Maximum amounts guaranteed by Con Edison totaled $859 million and $929 million at December 31, 2010 and 2009, respectively.
remediation at the site that the NYSDEC has required to date.
O&R is continuing a supplemental groundwater investigation and on-site vapor intrusion monitoring as required by the NYSDEC.
In 2011, NYSDEC initiated the reclassification process to list the site as properly closed but requiring continued management.
Newark Bay Approximately 300 parties, including O&R (which was served with a third-party complaint in June 2009), were sued as thirdparty defendants by Tierra Solutions, Inc.  (Tierra) and Maxus Energy Corporation (Maxus), successors to the Occidental Chemical Corporation and Diamond Shamrock Chemical Company.
Tierra and Maxus were themselves sued in 2005 by the New Jersey Department of Environmental Protection and others for removal and cleanup costs, punitive damages, penalties, and economic losses allegedly arising from the dioxin contamination their predecessors’ pesticide/herbicide plant allegedly released to the “Newark Bay Complex,” a system of waterways including Newark Bay, the Arthur Kill, the Kill Van Kull, and lower portions of the Passaic and Hackensack Rivers.
Tierra and Maxus are seeking equitable contribution from the thirdparty defendants for such costs, damages, penalties and losses, which are likely to be substantial.
As to O&R, Tierra and Maxus allege that 1975 and 1976 shipments of waste oil by O&R from an electricity generating plant in Haverstraw, New York to the Borne Chemical Company in Elizabeth, New Jersey was a source of petroleum discharges to the Arthur Kill.
Con Edison is unable to predict O&R’s exposure to liability with respect to the Newark Bay Complex.
Other Superfund Sites O&R is a PRP with respect to other Superfund sites where there are other PRPs and it is not managing the site investigation and remediation.
Work at these sites is in various stages, with the company participating in PRP groups at some of the sites.
Investigation, remediation and monitoring at some of these sites have been, and are expected to continue to be, conducted over extended periods of time.
The company does not believe that it is reasonably likely that monetary sanctions, such as penalties, will be imposed upon it by any governmental authority with respect to these sites.
The following table lists each of O&R’s other Superfund sites for which the company anticipates it may have liability.
The table also shows for each such site, its location, the year in which the company was designated or alleged to be a PRP or to otherwise have responsibilities with respect to the site (shown in the table under “Start”), the name of the court or agency in which proceedings with respect to the site are pending and O&R’s estimated percentage of total liability for each site.
The company currently estimates that its potential liability for investigation, remediation, monitoring and environmental damages at each site is less than $0.3 million.
Superfund liability is joint and several.
The company’s estimate of its anticipated share of the total liability for each site was determined pursuant to consent decrees, settlement agreements or otherwise and in light of the financial condition of other PRPs.
The company’s actual liability could differ substantially from amounts estimated.
## Table 3 ##
Other Federal, State and Local Environmental Provisions Toxic Substances Control Act Virtually all electric utilities, including CECONY, own equipment containing PCBs.
PCBs are regulated under the Federal Toxic Substances Control Act of 1976.
Water Quality Certain governmental authorities are investigating contamination in the Hudson River and the New York Harbor.
These waters run through portions of CECONY’s service area.
Governmental authorities could require entities that released hazardous substances that contaminated these waters to bear the cost of investigation and remediation, which could be substantial.
Air Quality Under new source review regulations, an owner of a large generating facility, including CECONY’s steam and steamelectric generating facilities, is required to obtain a permit before making modifications to the facility, other than routine maintenance, repair, or replacement, that increase emissions of pollutants from the facility above specified thresholds.
To obtain a permit, the facility owner could be required to install additional pollution controls or otherwise limit emissions from the facility.
The company reviews on an on-going basis its planned modifications to its generating facilities to determine the potential applicability of new source review and similar regulations.
In December 2011, the company filed its proposed plan to comply with revised New York State nitrogen oxides reasonably available control technology regulations.
In 2011, the EPA adopted regulations establishing maximum achievable control technology standards for utility and industrial boilers.
The regulations apply to major air emissions sources, including CECONY’s generating facilities.
In 2011, the EPA also adopted additional regulations known as the Cross State Air Pollution Rule, which established a new cap and trade program requiring further reductions in air emissions than the prior program (which will remain in effect pending a court-ordered stay of the new program).
CECONY’s plans to comply with the regulations include the modification by 2014 of certain of its generating facilities to enable the facilities to increase the use of natural gas, decreasing the use of fuel oil.
For information about the company’s generating facilities, see
M ANAGEMENT ’ S D ISCUSSION AND A NALYSIS OF F INANCIAL C ONDITION AND R ESULTS OF O PERATIONS – C ONTINUED operating expenses attributable to major storms in 2012 and 2011 were deferred as a regulatory asset.
See “Regulatory Assets and Liabilities” in Note B to the financial statements.
Gas CECONY’s results of gas operations for the year ended December 31, 2012 compared with the year ended December 31, 2011 is as follows
## Table 4 ##
CECONY’s gas sales and deliveries, excluding off-system sales, in 2012 compared with 2011 were
## Table 5 ##
(a) Includes 563 and 3,801 thousands of dths for 2012 and 2011, respectively, which are also reflected in firm transportation and othe CECONY’s gas operating revenues decreased $106 million in 2012 compared with 2011 due primarily to a decrease in gas purchased for resale costs ($131 million), offset in part higher revenues from the gas rate plan ($25 million).
CECONY’s revenues from gas sales are subject to a weather normalization clause and a revenue decoupling mechanism as a result of which delivery revenues are generally not affected by changes in delivery volumes from levels assumed when rates were approved.
Other gas operating revenues generally reflect changes in regulatory assets and liabilities in accordance with the company’s rate plans.
See Note B to the financial statements in Item 8.
CECONY’s sales and transportation volumes for firm customers decreased 7.2 percent in 2012 compared with 2011.
After adjusting for variations, principally weather and billing days, firm gas sales and transportation volumes in the company’s service area increased 0.6 percent in 2012.
CECONY’s purchased gas cost decreased $131 million in 2012 compared with 2011 due to lower unit costs ($120 million) and sendout volumes ($11 million).
CECONY’s gas operating income increased $51 million in 2012 compared with 2011.
The increase reflects primarily lower operations and maintenance expense ($36 million, due primarily to a decrease in the surcharges that are collected in revenues from customers ($34 million) and higher net revenues ($25 million), offset by higher depreciation and amortization ($10 million

<table><tr><td>Year Ended March 31,</td><td>Potential Dilutive Shares from Exercise of Common Stock Options</td></tr><tr><td>2001</td><td>1,808,322</td></tr><tr><td>2002</td><td>1,420,831</td></tr><tr><td>2003</td><td>58,343</td></tr></table>
<table><tr><td></td><td colspan="2"><i>Con Edison</i></td><td colspan="2"><i>Con Edison of New York</i></td><td colspan="2"><i>O&R</i></td></tr><tr><td><i>(Millions of Dollars)</i></td><td><i>2003</i></td><td><i>2002</i></td><td><i>2003</i></td><td><i>2002</i></td><td><i>2003</i></td><td><i>2002</i></td></tr><tr><td>Accrued Liabilities:</td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Manufactured gas plant sites</td><td>$145</td><td>$110</td><td>$106</td><td>$76</td><td>$39</td><td>$34</td></tr><tr><td>Other Superfund Sites</td><td>48</td><td>33</td><td>47</td><td>32</td><td>1</td><td>1</td></tr><tr><td>Total</td><td>$193</td><td>$143</td><td>$153</td><td>$108</td><td>$40</td><td>$35</td></tr><tr><td>Regulatory assets</td><td>$155</td><td>$83</td><td>$116</td><td>$52</td><td>$39</td><td>$31</td></tr></table>
<table><tr><td></td><td colspan="2"> Con Edison</td><td colspan="2"> CECONY</td></tr><tr><td><i></i> <i>(Millions of Dollars)</i></td><td> 2010</td><td> 2009</td><td> 2010</td><td> 2009</td></tr><tr><td>Accrued liability – asbestos suits</td><td>$10</td><td>$10</td><td>$10</td><td>$9</td></tr><tr><td>Regulatory assets – asbestos suits</td><td>$10</td><td>$10</td><td>$10</td><td>$9</td></tr><tr><td>Accrued liability – workers’ compensation</td><td>$106</td><td>$113</td><td>$101</td><td>$108</td></tr><tr><td>Regulatory assets – workers’ compensation</td><td>$31</td><td>$37</td><td>$31</td><td>$37</td></tr></table>
<table><tr><td> Site</td><td> Location</td><td> Start</td><td> Court or Agency</td><td> % of Total Liability</td></tr><tr><td>Borne Chemical</td><td>Elizabeth, NJ</td><td>1997</td><td>NJDEP</td><td>2.27%</td></tr><tr><td>Metal Bank of America</td><td>Philadelphia, PA</td><td>1993</td><td>EPA</td><td>4.58%</td></tr><tr><td>Ellis Road</td><td>Jacksonville, FL</td><td>2011</td><td>EPA</td><td>0.24%</td></tr></table>
<table><tr><td></td><td colspan="2"> Twelve Months Ended</td><td></td></tr><tr><td> (millions of dollars)</td><td> December 31, 2012</td><td> December 31, 2011</td><td>Variation</td></tr><tr><td>Operating revenues</td><td>$1,415</td><td>$1,521</td><td>$-106</td></tr><tr><td>Gas purchased for resale</td><td>387</td><td>518</td><td>-131</td></tr><tr><td>Net revenues</td><td>1,028</td><td>1,003</td><td>25</td></tr><tr><td>Operations and maintenance</td><td>330</td><td>366</td><td>-36</td></tr><tr><td>Depreciation and amortization</td><td>120</td><td>110</td><td>10</td></tr><tr><td>Taxes, other than income taxes</td><td>232</td><td>232</td><td>-</td></tr><tr><td> Gas operating income</td><td>$346</td><td>$295</td><td>$51</td></tr></table>
<table><tr><td></td><td colspan="4">Thousands of dths Delivered</td><td colspan="4">Revenues in Millions</td></tr><tr><td></td><td colspan="2"> Twelve Months Ended</td><td colspan="2"></td><td colspan="2">Twelve Months Ended</td><td colspan="2"></td></tr><tr><td> Description</td><td> December 31, 2012</td><td> December 31, 2011</td><td>Variation</td><td>Percent Variation</td><td> December 31, 2012</td><td>December 31, 2011</td><td>Variation</td><td>Percent Variation</td></tr><tr><td>Residential</td><td>33,457</td><td>38,160</td><td>-4,703</td><td>-12.3%</td><td>$607</td><td>$704</td><td>$-97</td><td>-13.8%</td></tr><tr><td>General</td><td>24,138</td><td>26,536</td><td>-2,398</td><td>-9.0</td><td>282</td><td>344</td><td>-62</td><td>-18.0</td></tr><tr><td>Firm transportation</td><td>52,860</td><td>54,291</td><td>-1,431</td><td>-2.6</td><td>380</td><td>356</td><td>24</td><td>6.7</td></tr><tr><td> Total firm sales and transportation</td><td> 110,455</td><td> 118,987</td><td>-8,532</td><td>-7.2</td><td>1,269</td><td>1,404</td><td>-135</td><td>-9.6</td></tr><tr><td>Interruptible sales<sup>(a)</sup></td><td>5,961</td><td>10,035</td><td>-4,074</td><td>-40.6</td><td>35</td><td>75</td><td>-40</td><td>-53.3</td></tr><tr><td>NYPA</td><td>48,107</td><td>34,893</td><td>13,214</td><td>37.9</td><td>2</td><td>2</td><td>-</td><td>-</td></tr><tr><td>Generation plants</td><td>85,827</td><td>75,207</td><td>10,620</td><td>14.1</td><td>32</td><td>32</td><td>-</td><td>-</td></tr><tr><td>Other</td><td>22,259</td><td>21,956</td><td>303</td><td>1.4</td><td>40</td><td>52</td><td>-12</td><td>-23.1</td></tr><tr><td>Other operating revenues</td><td>-</td><td>-</td><td>-</td><td>-</td><td>37</td><td>-44</td><td>81</td><td>Large</td></tr><tr><td> Total</td><td> 272,609</td><td> 261,078</td><td>11,531</td><td>4.4%</td><td>$1,415</td><td>$1,521</td><td>$-106</td><td>-7.0%</td></tr></table>

Question: what is the difference in amortized cost between 2002 and 2003?
Answer: -15777000