Reserves are reestimated quarterly, by combining historical results with current actual results to calculate new development factors.
This process incorporates the historic and latest actual trends, and other underlying changes in the data elements used to calculate reserve estimates.
New development factors are likely to differ from previous development factors used in prior reserve estimates because actual results (claims reported or settled, losses paid, or changes to case reserves) occur differently than the implied assumptions contained in the previous development factor calculations.
If claims reported, paid losses, or case reserve changes are greater or less than the levels estimated by previous development factors, reserve reestimates increase or decrease.
When actual development of these data elements is different than the historical development pattern used in a prior period reserve estimate, a new reserve is determined.
The difference between indicated reserves based on new reserve estimates and recorded reserves (the previous estimate) is the amount of reserve reestimate and is recognized as an increase or decrease in property-liability insurance claims and claims expense in the Consolidated Statements of Operations.
Total Property-liability reserve reestimates, after-tax, as a percent of net income in 2010, 2009 and 2008 were 11.1%, 8.5%, and (6.6)%, respectively.
For Property-Liability, the 3-year average of reserve reestimates as a percentage of total reserves was a favorable 0.2%, for Allstate Protection, the 3-year average of reserve estimates was a favorable 0.4% and for Discontinued Lines and Coverages, the 3-year average of reserve reestimates was an unfavorable 1.2%, each of these results being consistent within a reasonable actuarial tolerance for our respective businesses.
A more detailed discussion of reserve reestimates is presented in the Property-Liability Claims and Claims Expense Reserves section of this document.
The following table shows net claims and claims expense reserves by operating segment and line of business as of December 31:
## Table 0 ##
Allstate Protection reserve estimates Factors affecting reserve estimates Reserve estimates are developed based on the processes and historical development trends as previously described.
These estimates are considered in conjunction with known facts and interpretations of circumstances and factors including our experience with similar cases, actual claims paid, differing payment patterns and pending levels of unpaid claims, loss management programs, product mix and contractual terms, changes in law and regulation, judicial decisions, and economic conditions.
When we experience changes of the type previously mentioned, we may need to apply actuarial judgment in the determination and selection of development factors considered more reflective of the new trends, such as combining shorter or longer periods of historical results with current actual results to produce development factors based on two-year, three-year, or longer development periods to reestimate our reserves.
For example, if a legal change is expected to have a significant impact on the development of claim severity for a coverage which is part of a particular line of insurance in a specific state, actuarial judgment is applied to determine appropriate development factors that will most accurately reflect the expected impact on that specific estimate.
Another example would be when a change in economic conditions is expected to affect the cost of repairs to damaged autos or property for a particular line, coverage, or state, actuarial judgment is applied to determine appropriate development factors to use in the reserve estimate that will most accurately reflect the expected impacts on severity development.
As claims are reported, for certain liability claims of sufficient size and complexity, the field adjusting staff establishes case reserve estimates of ultimate cost, based on their assessment of facts and circumstances related to each individual claim.
For other claims which occur in large volumes and settle in a relatively short time frame, it is not practical or efficient to set case reserves for each claim, and a statistical case reserve is set for these claims based on estimation techniques previously described.
In the normal course of business, we may also supplement our claims
approximately 99% of the outstanding shares of common stock of Aon Corporation were held within the DTC system.
The Class A Ordinary Shares of Aon plc are, at present, eligible for deposit and clearing within the DTC system.
In connection with the closing of the Redomestication, we entered into arrangements with DTC whereby we agreed to indemnify DTC for any stamp duty and/or SDRT that may be assessed upon it as a result of its service as a depository and clearing agency for our Class A Ordinary Shares.
In addition, we have obtained a ruling from HMRC in respect of the stamp duty and SDRT consequences of the reorganization, and SDRT has been paid in accordance with the terms of this ruling in respect of the deposit of Class A Ordinary Shares with the initial depository.
DTC will generally have discretion to cease to act as a depository and clearing agency for the Class A Ordinary Shares.
If DTC determines at any time that the Class A Ordinary Shares are not eligible for continued deposit and clearance within its facilities, then we believe the Class A Ordinary Shares would not be eligible for continued listing on a U. S.  securities exchange or inclusion in the S&P 500 and trading in the Class A Ordinary Shares would be disrupted.
While we would pursue alternative arrangements to preserve our listing and maintain trading, any such disruption could have a material adverse effect on the trading price of the Class A Ordinary Shares.
Item 1B.
Unresolved Staff Comments.
None.
Item 2.
Properties.
We have offices in various locations throughout the world.
Substantially all of our offices are located in leased premises.
We maintain our corporate headquarters at 122 Leadenhall Street, London, England, where we occupy approximately 190,000 square feet of space under an operating lease agreement that expires in 2034.
We own one significant building at Pallbergweg 2-4, Amsterdam, the Netherlands (150,000 square feet).
The following are additional significant leased properties, along with the occupied square footage and expiration.
## Table 1 ##
The locations in Lincolnshire, Illinois, Gurgaon, India, The Woodlands, Texas, Orlando, Florida, and Charlotte, North Carolina, are primarily dedicated to our HR Solutions segment.
The other locations listed above house personnel from both of our reportable segments.
In general, no difficulty is anticipated in negotiating renewals as leases expire or in finding other satisfactory space if the premises become unavailable.
We believe that the facilities we currently occupy are adequate for the purposes for which they are being used and are well maintained.
In certain circumstances, we may have unused space and may seek to sublet such space to third parties, depending upon the demands for office space in the locations involved.
See Note 7 "Lease Commitments" of the Notes to Consolidated Financial Statements in Part II, Item 8 of this report for information with respect to our lease commitments as of December 31, 2015.
Item 3.
Legal Proceedings.
We hereby incorporate by reference Note 14 "Commitments and Contingencies" of the Notes to Consolidated Financial Statements in Part II, Item 8 of this report.
Item 4.
Mine Safety Disclosure.
Not applicable
MetLife, Inc.  Notes to the Consolidated Financial Statements — (Continued) Continuous Gross Unrealized Losses and OTTI Losses for Fixed Maturity and Equity Securities Available-for-Sale by Sector The following tables present the estimated fair value and gross unrealized losses of fixed maturity and equity securities in an unrealized loss position, aggregated by sector and by length of time that the securities have been in a continuous unrealized loss position.
The unrealized loss amounts presented below include the noncredit component of OTTI loss.
Fixed maturity securities on which a noncredit OTTI loss has been recognized in accumulated other comprehensive income (loss) are categorized by length of time as being “less than 12 months” or “equal to or greater than 12 months” in a continuous unrealized loss position based on the point in time that the estimated fair value initially declined to below the amortized cost basis and not the period of time since the unrealized loss was deemed a noncredit OTTI loss.
## Table 2 ##
December 31, 2010
## Table 3 ##
ROPER TECHNOLOGIES, INC.  AND SUBSIDIARIES NOTES TO CONSOLIDATED FINANCIAL STATEMENTS Years ended December 31, 2015, 2014 and 2013 (1) SUMMARY OF ACCOUNTING POLICIES Basis of Presentation—Effective April 24, 2015, Roper Industries, Inc.  changed its name to Roper Technologies, Inc.  in order to reflect its continued evolution to a diversified technology company.
These financial statements present consolidated information for Roper Technologies, Inc.  and its subsidiaries (“Roper” or the “Company”).
All significant intercompany accounts and transactions have been eliminated.
The Company has a minority investment which is not consolidated in its results.
The original investment, made in 2007, was $11.5 million.
During the year ended December 31, 2015, the Company determined, based on deterioration in earnings performance, that impairment of the investment was likely, and performed an estimated fair value calculation using an earnings multiples methodology.
The resulting value was determined to be $2 million, generating an impairment loss of $9.5 million which was reported as Other income/(expense) in the consolidated statement of earnings.
The December 31, 2014 consolidated balance sheet has been adjusted due to the retrospective early adoption of an accounting standard update (“ASU”) which requires that Roper’s senior notes be shown net of debt issuance costs.
The Other assets and Long-term debt, net of current portion line items on the December 31, 2014 consolidated balance sheet were reduced by $13 million.
The Company also early adopted the provisions of an ASU requiring deferred tax liabilities and assets to be classified as noncurrent in the consolidated balance sheet.
The ASU allowed for early adoption as of the beginning of an interim or annual reporting period, as well as the option to be applied either prospectively to all deferred tax liabilities and assets or retrospectively to all periods presented.
The Company elected to adopt on a prospective basis in the fourth quarter of 2015.
No prior periods were adjusted.
Nature of the Business—Roper is a diversified technology company.
The Company operates businesses that design and develop software (both license and software-as-a-service) and engineered products and solutions for a variety of niche end markets; including healthcare, transportation, food, energy, water, education and academic research.
Accounts Receivable—Accounts receivable are stated net of an allowance for doubtful accounts and sales allowances of $12.4 million and $13.7 million at December 31, 2015 and 2014, respectively.
Outstanding accounts receivable balances are reviewed periodically, and allowances are provided at such time that management believes it is probable that an account receivable is uncollectible.
The returns and other sales credit allowance is an estimate of customer returns, exchanges, discounts or other forms of anticipated concessions and is treated as a reduction in revenue.
Cash and Cash Equivalents—Roper considers highly liquid financial instruments with remaining maturities at acquisition of three months or less to be cash equivalents.
Roper had no cash equivalents at December 31, 2015 and $40 million at December 31, 2014.
Contingencies—Management continually assesses the probability of any adverse judgments or outcomes to its potential contingencies.
Disclosure of the contingency is made if there is at least a reasonable possibility that a loss or an additional loss may have been incurred.
In the assessment of contingencies as of December 31, 2015, management concluded that no accrual was necessary and that there were no matters for which there was a reasonable possibility of a material loss.
Earnings per Share—Basic earnings per share were calculated using net earnings and the weighted-average number of shares of common stock outstanding during the respective year.
Diluted earnings per share were calculated using net earnings and the weighted-average number of shares of common stock and potential common stock outstanding during the respective year.
Potentially dilutive common stock consisted of stock options and the premium over the conversion price on Roper’s senior subordinated convertible notes based upon the trading price of the Company’s common stock.
The effects of potential common stock were determined using the treasury stock method (in thousands):

<table><tr><td> ($ in millions) </td><td> 2010</td><td> 2009</td><td> 2008</td></tr><tr><td>Allstate Protection</td><td></td><td></td><td></td></tr><tr><td>Auto</td><td>$11,034</td><td>$10,606</td><td>$10,220</td></tr><tr><td>Homeowners</td><td>2,442</td><td>2,399</td><td>2,824</td></tr><tr><td>Other lines</td><td>2,141</td><td>2,145</td><td>2,207</td></tr><tr><td>Total Allstate Protection</td><td>15,617</td><td>15,150</td><td>15,251</td></tr><tr><td>Discontinued Lines and Coverages</td><td></td><td></td><td></td></tr><tr><td>Asbestos</td><td>1,100</td><td>1,180</td><td>1,228</td></tr><tr><td>Environmental</td><td>201</td><td>198</td><td>195</td></tr><tr><td>Other discontinued lines</td><td>478</td><td>500</td><td>508</td></tr><tr><td>Total Discontinued Lines and Coverages</td><td>1,779</td><td>1,878</td><td>1,931</td></tr><tr><td>Total Property-Liability</td><td>$17,396</td><td>$17,028</td><td>$17,182</td></tr></table>
<table><tr><td>Property:</td><td>OccupiedSquare Footage</td><td>LeaseExpiration Dates</td></tr><tr><td>4 Overlook Point and other locations, Lincolnshire, Illinois</td><td>1,059,000</td><td>2019 – 2024</td></tr><tr><td>Tikri Campus and Unitech Cyber Park, Gurgaon, India</td><td>440,000</td><td>2015 – 2019</td></tr><tr><td>200 E. Randolph Street, Chicago, Illinois</td><td>428,000</td><td>2028</td></tr><tr><td>2601 Research Forest Drive, The Woodlands, Texas</td><td>414,000</td><td>2020</td></tr><tr><td>2300 Discovery Drive, Orlando, Florida</td><td>364,000</td><td>2020</td></tr><tr><td>199 Water Street, New York, New York</td><td>319,000</td><td>2018</td></tr><tr><td>7201 Hewitt Associates Drive, Charlotte, North Carolina</td><td>218,000</td><td>2025</td></tr></table>
<table><tr><td></td><td colspan="6"> December 31, 2011</td></tr><tr><td></td><td colspan="2"> Less than 12 Months</td><td colspan="2"> Equal to or Greater than 12 Months</td><td colspan="2"> Total</td></tr><tr><td></td><td> Estimated Fair  Value</td><td> Gross Unrealized Losses</td><td> Estimated Fair  Value</td><td> Gross Unrealized Losses</td><td> Estimated Fair  Value</td><td> Gross Unrealized Losses</td></tr><tr><td></td><td colspan="6"> (In millions, except number of securities)</td></tr><tr><td> Fixed Maturity Securities:</td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>U.S. corporate securities</td><td>$15,642</td><td>$590</td><td>$5,135</td><td>$790</td><td>$20,777</td><td>$1,380</td></tr><tr><td>Foreign corporate securities</td><td>12,618</td><td>639</td><td>5,957</td><td>700</td><td>18,575</td><td>1,339</td></tr><tr><td>Foreign government securities</td><td>11,227</td><td>230</td><td>1,799</td><td>127</td><td>13,026</td><td>357</td></tr><tr><td>RMBS</td><td>4,040</td><td>547</td><td>4,724</td><td>1,189</td><td>8,764</td><td>1,736</td></tr><tr><td>U.S. Treasury and agency securities</td><td>2,611</td><td>1</td><td>50</td><td>1</td><td>2,661</td><td>2</td></tr><tr><td>CMBS</td><td>2,825</td><td>135</td><td>678</td><td>91</td><td>3,503</td><td>226</td></tr><tr><td>State and political subdivision securities</td><td>177</td><td>2</td><td>1,007</td><td>154</td><td>1,184</td><td>156</td></tr><tr><td>ABS</td><td>4,972</td><td>103</td><td>1,316</td><td>214</td><td>6,288</td><td>317</td></tr><tr><td>Other fixed maturity securities</td><td>—</td><td>—</td><td>—</td><td>—</td><td>—</td><td>—</td></tr><tr><td>Total fixed maturity securities</td><td>$54,112</td><td>$2,247</td><td>$20,666</td><td>$3,266</td><td>$74,778</td><td>$5,513</td></tr><tr><td> Equity Securities:</td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Common stock</td><td>$581</td><td>$96</td><td>$5</td><td>$1</td><td>$586</td><td>$97</td></tr><tr><td>Non-redeemable preferred stock</td><td>204</td><td>30</td><td>370</td><td>172</td><td>574</td><td>202</td></tr><tr><td>Total equity securities</td><td>$785</td><td>$126</td><td>$375</td><td>$173</td><td>$1,160</td><td>$299</td></tr><tr><td>Total number of securities in an unrealized loss position</td><td>3,978</td><td></td><td>1,963</td><td></td><td></td><td></td></tr></table>
<table><tr><td></td><td colspan="6"> December 31, 2010</td></tr><tr><td></td><td colspan="2"> Less than 12 Months</td><td colspan="2"> Equal to or Greater  than 12Months</td><td colspan="2"> Total</td></tr><tr><td></td><td> Estimated Fair  Value</td><td> Gross Unrealized Losses</td><td> Estimated Fair  Value</td><td> Gross Unrealized Losses</td><td> Estimated Fair  Value</td><td> Gross Unrealized Losses</td></tr><tr><td></td><td colspan="6"> (In millions, except number of securities)</td></tr><tr><td> Fixed Maturity Securities:</td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>U.S. corporate securities</td><td>$22,954</td><td>$447</td><td>$8,319</td><td>$1,155</td><td>$31,273</td><td>$1,602</td></tr><tr><td>Foreign corporate securities</td><td>22,415</td><td>410</td><td>3,976</td><td>515</td><td>26,391</td><td>925</td></tr><tr><td>Foreign government securities</td><td>26,659</td><td>585</td><td>189</td><td>17</td><td>26,848</td><td>602</td></tr><tr><td>RMBS</td><td>7,630</td><td>221</td><td>7,624</td><td>1,492</td><td>15,254</td><td>1,713</td></tr><tr><td>U.S. Treasury and agency securities</td><td>13,401</td><td>530</td><td>118</td><td>29</td><td>13,519</td><td>559</td></tr><tr><td>CMBS</td><td>3,787</td><td>29</td><td>1,363</td><td>249</td><td>5,150</td><td>278</td></tr><tr><td>State and political subdivision securities</td><td>5,061</td><td>246</td><td>988</td><td>272</td><td>6,049</td><td>518</td></tr><tr><td>ABS</td><td>2,671</td><td>33</td><td>2,102</td><td>350</td><td>4,773</td><td>383</td></tr><tr><td>Other fixed maturity securities</td><td>1</td><td>—</td><td>—</td><td>—</td><td>1</td><td>—</td></tr><tr><td>Total fixed maturity securities</td><td>$104,579</td><td>$2,501</td><td>$24,679</td><td>$4,079</td><td>$129,258</td><td>$6,580</td></tr><tr><td> Equity Securities:</td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Common stock</td><td>$89</td><td>$12</td><td>$1</td><td>$—</td><td>$90</td><td>$12</td></tr><tr><td>Non-redeemable preferred stock</td><td>191</td><td>9</td><td>824</td><td>220</td><td>1,015</td><td>229</td></tr><tr><td>Total equity securities</td><td>$280</td><td>$21</td><td>$825</td><td>$220</td><td>$1,105</td><td>$241</td></tr><tr><td>Total number of securities in an unrealized loss position</td><td>5,609</td><td></td><td>1,704</td><td></td><td></td><td></td></tr></table>

Question: how many years are left till the lease expiration date for the building of aon's corporate headquarters?
Answer: 19