NOTES TO CONSOLIDATED FINANCIAL STATEMENTS (Continued) Note 2—Financial Instruments (Continued) covered by collateral, third-party flooring arrangements, or credit insurance are outstanding with the Company’s distribution and retail channel partners.
One customer accounted for approximately 11% of trade receivables as of September 29, 2007, while no customers accounted for more than 10% of trade receivables as of September 30, 2006.
The following table summarizes the activity in the allowance for doubtful accounts (in millions):
## Table 0 ##
Vendor Non-Trade Receivables The Company has non-trade receivables from certain of its manufacturing vendors resulting from the sale of raw material components to these manufacturing vendors who manufacture sub-assemblies or assemble final products for the Company.
The Company purchases these raw material components directly from suppliers.
These non-trade receivables, which are included in the Consolidated Balance Sheets in other current assets, totaled $2.4 billion and $1.6 billion as of September 29, 2007 and September 30, 2006, respectively.
The Company does not reflect the sale of these components in net sales and does not recognize any profits on these sales until the products are sold through to the end customer at which time the profit is recognized as a reduction of cost of sales.
Derivative Financial Instruments The Company uses derivatives to partially offset its business exposure to foreign exchange risk.
Foreign currency forward and option contracts are used to offset the foreign exchange risk on certain existing assets and liabilities and to hedge the foreign exchange risk on expected future cash flows on certain forecasted revenue and cost of sales.
The Company’s accounting policies for these instruments are based on whether the instruments are designated as hedge or non-hedge instruments.
The Company records all derivatives on the balance sheet at fair value.
CF INDUSTRIES HOLDINGS, INC.  As a result of reduced operating rates in 2005, both the Donaldsonville and Medicine Hat nitrogen fertilizer complexes consumed less gas than if they had operated at capacity.
In 2005, the Donaldsonville nitrogen fertilizer complex consumed approximately 63 billion cubic feet of natural gas.
Operating at capacity, this facility would consume approximately 80 billion cubic feet of natural gas.
The facility has access to five natural gas pipelines and obtains gas from several suppliers.
In 2005, the largest individual supplier provided approximately 38% of the Donaldsonville facility’s total gas requirement.
The Medicine Hat complex consumed approximately 37 billion cubic feet of natural gas in 2005.
Operating at capacity this facility would consume approximately 46 billion cubic feet of natural gas.
The facility has access to two natural gas pipelines and obtains gas from numerous suppliers, the largest of which supplied approximately 39% of gas consumption in 2005.
Nitrogen Fertilizer Distribution The Donaldsonville nitrogen fertilizer complex, which is located on the Mississippi River, includes a deep-water docking facility, access to an ammonia shipping pipeline and truck and railroad loading capabilities.
The Medicine Hat nitrogen fertilizer complex ships our share of ammonia and urea by truck and rail to customers in the United States and Canada and to our storage facilities in the northern United States.
Ammonia, urea and UAN from Donaldsonville can be loaded into ocean-going vessels and river barges for direct shipment to domestic customers, transport to storage facilities, or export.
We own six ammonia river barges with a total capacity of 16,400 tons.
We contract on a dedicated basis for tug services and the operation of these barges.
We also contract on a dedicated basis 16 UAN river barges with a total capacity of approximately 48,000 tons.
Additional ammonia and UAN barge capacity is contracted for as needed.
River transportation for urea is provided primarily under an agreement with one of the major inland river system barge operators.
The Donaldsonville facility is connected to the Valero Ammonia Pipeline.
This 2,000-mile long ammonia pipeline is used by several nitrogen producers to transport ammonia to over 20 terminals and shipping points located in the midwestern U. S.  cornbelt.
We are a major customer of this ammonia pipeline.
In 2005, approximately 53% of our ammonia shipments from our Donaldsonville nitrogen fertilizer complex were transported via the ammonia pipeline.
We also transport substantial volumes of urea and UAN from the Donaldsonville nitrogen fertilizer complex and ammonia and urea from the Medicine Hat nitrogen fertilizer complex by rail.
In addition to rail cars provided by the rail carriers, we currently lease 552 ammonia tank cars, 1,010 UAN tank cars and 613 dry product hopper cars.
Phosphate Fertilizer Business We are a major manufacturer of phosphate fertilizer products.
Our main phosphate fertilizer products are DAP and MAP.
Our historical sales of phosphate fertilizer products are shown in the table below.
## Table 1 ##
(1) Other phosphate fertilizer products include sulfuric acid, GTSP (granular triple superphosphate) and feed phosphates.
CF INDUSTRIES HOLDINGS, INC.  53 Granular Urea Segment Our granular urea segment produces granular urea, which contains 46% nitrogen.
Produced from ammonia and carbon dioxide, it has the highest nitrogen content of any of our solid nitrogen fertilizers.
Granular urea is produced at our Courtright, Ontario; Donaldsonville, Louisiana; Medicine Hat, Alberta; and Port Neal, Iowa nitrogen complexes.
The following table presents summary operating data for our granular urea segment:
## Table 2 ##
(1) Granular urea represents 46% nitrogen content.
Nutrient tons represent the tons of nitrogen within the product tons.
Year Ended December 31, 2016 Compared to Year Ended December 31, 2015 Net Sales.
Net sales in the granular urea segment increased by $43 million, or 5%, in 2016 compared to 2015 due primarily to a 46% increase in sales volume partially offset by a 28% decrease in average selling prices.
Sales volume was higher due to increased production available as a result of our expanded urea capacity at our Donaldsonville, Louisiana complex that came on line in November of 2015.
Average selling prices decreased to $231 per ton in 2016 compared to $320 per ton in 2015 due primarily to excess global nitrogen supply weighing on global nitrogen fertilizer selling prices.
Cost of Sales.
Cost of sales per ton in our granular urea segment averaged $162 in 2016, a 15% decrease from the $191 per ton in 2015.
The decrease was due primarily to the impact of unrealized net mark-to-market gains on natural gas derivatives in 2016 compared to losses in 2015.
This was partly offset by increased depreciation expense related to our expanded urea production at our Donaldsonville, Louisiana complex and $2 million of start-up costs at our Port Neal, Iowa complex that came on line in December 2016.
Year Ended December 31, 2015 Compared to Year Ended December 31, 2014 Net Sales.
Net sales in the granular urea segment decreased by $127 million, or 14%, for 2015 compared to 2014 due primarily to a 14% decrease in average selling prices.
Average selling prices decreased to $320 per ton in 2015 compared to $372 per ton in 2014 due primarily to excess global nitrogen supply weighing on global nitrogen fertilizer selling prices.
Granular urea exports from China were at a record high in 2015 and Russian exports had increased significantly while global capacity additions in 2015 further contributed to the excess global nitrogen supply.
Our sales volume in 2015 was flat compared to the prior year as we offset weaker domestic demand with sales out of our new urea production at our Donaldsonville, Louisiana complex that came on line in November 2015.
Cost of Sales.
Cost of sales per ton in our granular urea segment averaged $191 in 2015, a 9% decrease over the $210 per ton in 2014.
The decrease was due primarily to lower realized natural gas costs partly offset by the impact of increased unrealized net mark-to-market losses on natural gas derivatives in 2015 compared to 2014.

Tables referenced above, in order (Table 0 first):
<table><tr><td></td><td>September 29, 2007</td><td>September 30, 2006</td><td>September 24, 2005</td></tr><tr><td>Beginning allowance balance</td><td>$52</td><td>$46</td><td>$47</td></tr><tr><td>Charged to costs and expenses</td><td>12</td><td>17</td><td>8</td></tr><tr><td>Deductions</td><td>-17</td><td>-11</td><td>-9</td></tr><tr><td>Ending allowance balance</td><td>$47</td><td>$52</td><td>$46</td></tr></table>
<table><tr><td> </td><td colspan="2"> 2005</td><td colspan="2"> 2004</td><td colspan="2"> 2003</td></tr><tr><td> </td><td> Tons</td><td> Net Sales</td><td> Tons</td><td> Net Sales</td><td> Tons</td><td> Net Sales</td></tr><tr><td> </td><td colspan="6"> (tons in thousands; dollars in millions)  </td></tr><tr><td>Phosphate Fertilizer Products</td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>DAP</td><td>1,583</td><td>$343.8</td><td>1,549</td><td>$305.3</td><td>1,627</td><td>$264.4</td></tr><tr><td>MAP</td><td>426</td><td>94.9</td><td>351</td><td>71.5</td><td>252</td><td>43.3</td></tr><tr><td>Other phosphate fertilizers<sup>-1</sup></td><td>—</td><td>—</td><td>—</td><td>—</td><td>13</td><td>2.1</td></tr><tr><td>Total</td><td>2,009</td><td>$438.7</td><td>1,900</td><td>$376.8</td><td>1,892</td><td>$309.8</td></tr></table>
<table><tr><td></td><td colspan="7">Twelve months ended December 31,</td></tr><tr><td></td><td>2016</td><td>2015</td><td>2014</td><td colspan="2">2016 v. 2015</td><td colspan="2">2015 v. 2014</td></tr><tr><td></td><td colspan="7">(in millions, except as noted)</td></tr><tr><td>Net sales</td><td>$831</td><td>$788</td><td>$915</td><td>$43</td><td>5%</td><td>$-127</td><td>-14%</td></tr><tr><td>Cost of sales</td><td>584</td><td>469</td><td>517</td><td>115</td><td>25%</td><td>-48</td><td>-9%</td></tr><tr><td>Gross margin</td><td>$247</td><td>$319</td><td>$398</td><td>$-72</td><td>-23%</td><td>$-79</td><td>-20%</td></tr><tr><td>Gross margin percentage</td><td>29.7%</td><td>40.4%</td><td>43.5%</td><td>-10.7%</td><td></td><td>-3.1%</td><td></td></tr><tr><td>Sales volume by product tons (000s)</td><td>3,597</td><td>2,460</td><td>2,459</td><td>1,137</td><td>46%</td><td>1</td><td>—%</td></tr><tr><td>Sales volume by nutrient tons (000s)<sup>(1)</sup></td><td>1,654</td><td>1,132</td><td>1,131</td><td>522</td><td>46%</td><td>1</td><td>—%</td></tr><tr><td>Average selling price per product ton</td><td>$231</td><td>$320</td><td>$372</td><td>$-89</td><td>-28%</td><td>$-52</td><td>-14%</td></tr><tr><td>Average selling price per nutrient ton<sup>-1</sup></td><td>$502</td><td>$696</td><td>$809</td><td>$-194</td><td>-28%</td><td>$-113</td><td>-14%</td></tr><tr><td>Gross margin per product ton</td><td>$69</td><td>$129</td><td>$162</td><td>$-60</td><td>-47%</td><td>$-33</td><td>-20%</td></tr><tr><td>Gross margin per nutrient ton<sup>-1</sup></td><td>$149</td><td>$281</td><td>$352</td><td>$-132</td><td>-47%</td><td>$-71</td><td>-20%</td></tr><tr><td>Depreciation and amortization</td><td>$112</td><td>$51</td><td>$37</td><td>$61</td><td>120%</td><td>$14</td><td>38%</td></tr><tr><td>Unrealized net mark-to-market loss (gain) on natural gas derivatives</td><td>$-67</td><td>$47</td><td>$17</td><td>$-114</td><td>N/M</td><td>$30</td><td>176%</td></tr></table>

Question: what was the percentage change in the allowance for doubtful accounts from 2005 to 2006?
Answer: 0.13043
Reasoning program: subtract(52,46), divide(#0,46)