incentive compensation expense ( $ 8.2 million ) and related fringe benefit costs ( $ 1.4 million ) , and higher warehousing costs due to customer requirements ( $ 2.0 million ) .corporate overhead for the year ended december 31 , 2006 , increased $ 3.1 million , or 6.5% ( 6.5 % ) , from the year ended december 31 , 2005 .the increase was primarily attributable to higher incentive compensation expense ( $ 2.6 million ) and other increased costs which were not individually significant .other expense , net , decreased $ 2.1 million , or 20.1% ( 20.1 % ) for the year ended december 31 , 2006 compared to the year ended december 31 , 2005 .the decrease was primarily due to a $ 3.1 million decrease in expenses related to the disposals of property , plant and equipment as part of planned disposals in connection with capital projects .partially offsetting the decrease in fixed asset disposal expense was higher legal expenses ( $ 0.5 million ) and increased losses on disposals of storeroom items ( $ 0.4 million ) .interest expense , net and income taxes interest expense , net of interest income , increased by $ 3.1 million , or 11.1% ( 11.1 % ) , for the year ended december 31 , 2006 compared to the full year 2005 , primarily as a result of higher interest expense on our variable rate debt due to higher interest rates .pca 2019s effective tax rate was 35.8% ( 35.8 % ) for the year ended december 31 , 2006 and 40.2% ( 40.2 % ) for the year ended december 31 , 2005 .the lower tax rate in 2006 is primarily due to a larger domestic manufacturer 2019s deduction and a reduction in the texas state tax rate .for both years 2006 and 2005 , tax rates were higher than the federal statutory rate of 35.0% ( 35.0 % ) due to state income taxes .year ended december 31 , 2005 compared to year ended december 31 , 2004 the historical results of operations of pca for the years ended december 31 , 2005 and 2004 are set forth below : for the year ended december 31 , ( in millions ) 2005 2004 change .
[['( in millions )', 'for the year ended december 31 , 2005', 'for the year ended december 31 , 2004', 'change'], ['net sales', '$ 1993.7', '$ 1890.1', '$ 103.6'], ['income from operations', '$ 116.1', '$ 140.5', '$ -24.4 ( 24.4 )'], ['interest expense net', '-28.1 ( 28.1 )', '-29.6 ( 29.6 )', '1.5'], ['income before taxes', '88.0', '110.9', '-22.9 ( 22.9 )'], ['provision for income taxes', '-35.4 ( 35.4 )', '-42.2 ( 42.2 )', '6.8'], ['net income', '$ 52.6', '$ 68.7', '$ -16.1 ( 16.1 )']]
net sales net sales increased by $ 103.6 million , or 5.5% ( 5.5 % ) , for the year ended december 31 , 2005 from the year ended december 31 , 2004 .net sales increased primarily due to increased sales prices and volumes of corrugated products compared to 2004 .total corrugated products volume sold increased 4.2% ( 4.2 % ) to 31.2 billion square feet in 2005 compared to 29.9 billion square feet in 2004 .on a comparable shipment-per-workday basis , corrugated products sales volume increased 4.6% ( 4.6 % ) in 2005 from 2004 .excluding pca 2019s acquisition of midland container in april 2005 , corrugated products volume was 3.0% ( 3.0 % ) higher in 2005 than 2004 and up 3.4% ( 3.4 % ) compared to 2004 on a shipment-per-workday basis .shipments-per-workday is calculated by dividing our total corrugated products volume during the year by the number of workdays within the year .the larger percentage increase was due to the fact that 2005 had one less workday ( 250 days ) , those days not falling on a weekend or holiday , than 2004 ( 251 days ) .containerboard sales volume to external domestic and export customers decreased 12.2% ( 12.2 % ) to 417000 tons for the year ended december 31 , 2005 from 475000 tons in 2004. .

Question: pca 2019s effective tax rate decreased by how many percentage points for the year ended december 31 , 2006 compared to the year ended december 31 , 2005?
Answer: 4.4