entergy texas , inc . management's financial discussion and analysis fuel and purchased power expenses increased primarily due to an increase in power purchases as a result of the purchased power agreements between entergy gulf states louisiana and entergy texas and an increase in the average market prices of purchased power and natural gas , substantially offset by a decrease in deferred fuel expense as a result of decreased recovery from customers of fuel costs . other regulatory charges increased primarily due to an increase of $ 6.9 million in the recovery of bond expenses related to the securitization bonds . the recovery became effective july 2007 . see note 5 to the financial statements for additional information regarding the securitization bonds . 2007 compared to 2006 net revenue consists of operating revenues net of : 1 ) fuel , fuel-related expenses , and gas purchased for resale , 2 ) purchased power expenses , and 3 ) other regulatory charges . following is an analysis of the change in net revenue comparing 2007 to 2006 . amount ( in millions ) .
what percent of the net change in revenue between 2006 and 2007 was due to transmission revenue?
the purchased power capacity variance is due to changes in the purchased power capacity costs included in the calculation in 2007 compared to 2006 used to bill generation costs between entergy texas and entergy gulf states louisiana . the securitization transition charge variance is due to the issuance of securitization bonds . as discussed above , in june 2007 , egsrf i , a company wholly-owned and consolidated by entergy texas , issued securitization bonds and with the proceeds purchased from entergy texas the transition property , which is the right to recover from customers through a transition charge amounts sufficient to service the securitization bonds . see note 5 to the financial statements herein for details of the securitization bond issuance . the volume/weather variance is due to increased electricity usage on billed retail sales , including the effects of more favorable weather in 2007 compared to the same period in 2006 . the increase is also due to an increase in usage during the unbilled sales period . retail electricity usage increased a total of 139 gwh in all sectors . see "critical accounting estimates" below and note 1 to the financial statements for further discussion of the accounting for unbilled revenues . the transmission revenue variance is due to an increase in rates effective june 2007 and new transmission customers in late 2006 . the base revenue variance is due to the transition to competition rider that began in march 2006 . refer to note 2 to the financial statements for further discussion of the rate increase . gross operating revenues , fuel and purchased power expenses , and other regulatory charges gross operating revenues decreased primarily due to a decrease of $ 179 million in fuel cost recovery revenues due to lower fuel rates and fuel refunds . the decrease was partially offset by the $ 39 million increase in net revenue described above and an increase of $ 44 million in wholesale revenues , including $ 30 million from the system agreement cost equalization payments from entergy arkansas . the receipt of such payments is being .