higher average borrowings . additionally , the recapitalization that occurred late in the first quarter of 2005 resulted in a full year of interest in 2006 as compared to approximately ten months in 2005 . the increase in interest expense in 2005 as compared to 2004 also resulted from the recapitalization in 2005 . income tax expense income tax expense totaled $ 150.2 million , $ 116.1 million and $ 118.3 million for 2006 , 2005 and 2004 , respectively . this resulted in an effective tax rate of 37.2% ( 37.2 % ) , 37.2% ( 37.2 % ) and 37.6% ( 37.6 % ) for 2006 , 2005 and 2004 , respectively . net earnings net earnings totaled $ 259.1 million , $ 196.6 and $ 189.4 million for 2006 , 2005 and 2004 , respectively , or $ 1.37 , $ 1.53 and $ 1.48 per diluted share , respectively . segment results of operations transaction processing services ( in thousands ) .
what was the percentage change in operating income from 2005 to 2006?
revenues for the transaction processing services segment are derived from three main revenue channels ; enterprise solutions , integrated financial solutions and international . revenues from transaction processing services totaled $ 2458.8 million , $ 1208.4 and $ 892.0 million for 2006 , 2005 and 2004 , respectively . the overall segment increase of $ 1250.4 million during 2006 , as compared to 2005 was primarily attributable to the certegy merger which contributed $ 1067.2 million to the overall increase . the majority of the remaining 2006 growth is attributable to organic growth within the historically owned integrated financial solutions and international revenue channels , with international including $ 31.9 million related to the newly formed business process outsourcing operation in brazil . the overall segment increase of $ 316.4 in 2005 as compared to 2004 results from the inclusion of a full year of results for the 2004 acquisitions of aurum , sanchez , kordoba , and intercept , which contributed $ 301.1 million of the increase . cost of revenues for the transaction processing services segment totaled $ 1914.1 million , $ 904.1 million and $ 667.1 million for 2006 , 2005 and 2004 , respectively . the overall segment increase of $ 1010.0 million during 2006 as compared to 2005 was primarily attributable to the certegy merger which contributed $ 848.2 million to the increase . gross profit as a percentage of revenues ( 201cgross margin 201d ) was 22.2% ( 22.2 % ) , 25.2% ( 25.2 % ) and 25.2% ( 25.2 % ) for 2006 , 2005 and 2004 , respectively . the decrease in gross profit in 2006 as compared to 2005 is primarily due to the february 1 , 2006 certegy merger , which businesses typically have lower margins than those of the historically owned fis businesses . incremental intangible asset amortization relating to the certegy merger also contributed to the decrease in gross margin . included in cost of revenues was depreciation and amortization of $ 272.4 million , $ 139.8 million , and $ 94.6 million for 2006 , 2005 and 2004 , respectively . selling , general and administrative expenses totaled $ 171.1 million , $ 94.9 million and $ 99.6 million for 2006 , 2005 and 2004 , respectively . the increase in 2006 compared to 2005 is primarily attributable to the certegy merger which contributed $ 73.7 million to the overall increase of $ 76.2 million . the decrease of $ 4.7 million in 2005 as compared to 2004 is primarily attributable to the effect of acquisition related costs in 2004 . included in selling , general and administrative expenses was depreciation and amortization of $ 11.0 million , $ 9.1 million and $ 2.3 million for 2006 , 2005 and 2004 , respectively. .