Financial report context:
reinsurance commissions , fees and other revenue increased 1% ( 1 % ) driven by a favorable foreign currency translation of 2% ( 2 % ) and was partially offset by a 1% ( 1 % ) decline in dispositions , net of acquisitions and other . organic revenue was flat primarily resulting from strong growth in the capital market transactions and advisory business , partially offset by declines in global facultative placements . operating income operating income increased $ 120 million , or 10% ( 10 % ) , from 2010 to $ 1.3 billion in 2011 . in 2011 , operating income margins in this segment were 19.3% ( 19.3 % ) , up 70 basis points from 18.6% ( 18.6 % ) in 2010 . operating margin improvement was primarily driven by revenue growth , reduced costs of restructuring initiatives and realization of the benefits of those restructuring plans , which was partially offset by the negative impact of expense increases related to investment in the business , lease termination costs , legacy receivables write-off , and foreign currency exchange rates . hr solutions .

Financial table:
years ended december 31,: revenue; 2011: $ 4501; 2010: $ 2111; 2009: $ 1267
years ended december 31,: operating income; 2011: 448; 2010: 234; 2009: 203
years ended december 31,: operating margin; 2011: 10.0% ( 10.0 % ); 2010: 11.1% ( 11.1 % ); 2009: 16.0% ( 16.0 % )

Additional report context:
in october 2010 , we completed the acquisition of hewitt , one of the world 2019s leading human resource consulting and outsourcing companies . hewitt operates globally together with aon 2019s existing consulting and outsourcing operations under the newly created aon hewitt brand . hewitt 2019s operating results are included in aon 2019s results of operations beginning october 1 , 2010 . our hr solutions segment generated approximately 40% ( 40 % ) of our consolidated total revenues in 2011 and provides a broad range of human capital services , as follows : 2022 health and benefits advises clients about how to structure , fund , and administer employee benefit programs that attract , retain , and motivate employees . benefits consulting includes health and welfare , executive benefits , workforce strategies and productivity , absence management , benefits administration , data-driven health , compliance , employee commitment , investment advisory and elective benefits services . effective january 1 , 2012 , this line of business will be included in the results of the risk solutions segment . 2022 retirement specializes in global actuarial services , defined contribution consulting , investment consulting , tax and erisa consulting , and pension administration . 2022 compensation focuses on compensatory advisory/counsel including : compensation planning design , executive reward strategies , salary survey and benchmarking , market share studies and sales force effectiveness , with special expertise in the financial services and technology industries . 2022 strategic human capital delivers advice to complex global organizations on talent , change and organizational effectiveness issues , including talent strategy and acquisition , executive on-boarding , performance management , leadership assessment and development , communication strategy , workforce training and change management . 2022 benefits administration applies our hr expertise primarily through defined benefit ( pension ) , defined contribution ( 401 ( k ) ) , and health and welfare administrative services . our model replaces the resource-intensive processes once required to administer benefit plans with more efficient , effective , and less costly solutions . 2022 human resource business processing outsourcing ( 2018 2018hr bpo 2019 2019 ) provides market-leading solutions to manage employee data ; administer benefits , payroll and other human resources processes ; and .

Question: what is the highest revenue observed in this period?
Answer: 4501