CF INDUSTRIES HOLDINGS, INC.  118 16.
Derivative Financial Instruments We use derivative financial instruments to reduce our exposure to changes in commodity prices and foreign currency exchange rates.
Commodity Price Risk Management Natural gas is the largest and most volatile component of the manufacturing cost for nitrogen-based products.
We manage the risk of changes in natural gas prices primarily through the use of derivative financial instruments covering periods through the end of 2018.
The derivatives that we use are primarily fixed price swaps and options traded in the OTC markets.
These natural gas derivatives settle using primarily a NYMEX futures price index, which represents the basis for fair value at any given time.
We entered into natural gas derivative contracts with respect to natural gas to be consumed by us in the future, and settlements of those derivative contracts are scheduled to coincide with our anticipated purchases of natural gas used to manufacture nitrogen products during those future periods.
We use natural gas derivatives as an economic hedge of natural gas price risk, but without the application of hedge accounting.
As a result, changes in fair value of these contracts are recognized in earnings.
As of December 31, 2015 and 2014, we had open natural gas derivative contracts for 431.5 million MMBtus and 58.7 million MMBtus, respectively.
For the year ended December 31, 2015, we used derivatives to cover approximately 64% of our natural gas consumption.
Foreign Currency Exchange Rates In the fourth quarter of 2012, our Board of Directors authorized a project to construct new ammonia and urea/UAN plants at our Donaldsonville, Louisiana complex and new ammonia and urea plants at our Port Neal, Iowa complex.
A portion of the capacity expansion project costs are euro-denominated.
In order to manage our exposure to changes in the euro to U. S.  dollar currency exchange rates, we have hedged our projected euro-denominated payments through the third quarter of 2016 using foreign currency forward contracts.
CF INDUSTRIES HOLDINGS, INC.  118 16.
Derivative Financial Instruments We use derivative financial instruments to reduce our exposure to changes in commodity prices and foreign currency exchange rates.
Commodity Price Risk Management Natural gas is the largest and most volatile component of the manufacturing cost for nitrogen-based products.
We manage the risk of changes in natural gas prices primarily through the use of derivative financial instruments covering periods through the end of 2018.
The derivatives that we use are primarily fixed price swaps and options traded in the OTC markets.
These natural gas derivatives settle using primarily a NYMEX futures price index, which represents the basis for fair value at any given time.
We entered into natural gas derivative contracts with respect to natural gas to be consumed by us in the future, and settlements of those derivative contracts are scheduled to coincide with our anticipated purchases of natural gas used to manufacture nitrogen products during those future periods.
We use natural gas derivatives as an economic hedge of natural gas price risk, but without the application of hedge accounting.
As a result, changes in fair value of these contracts are recognized in earnings.
As of December 31, 2015 and 2014, we had open natural gas derivative contracts for 431.5 million MMBtus and 58.7 million MMBtus, respectively.
For the year ended December 31, 2015, we used derivatives to cover approximately 64% of our natural gas consumption.
Foreign Currency Exchange Rates In the fourth quarter of 2012, our Board of Directors authorized a project to construct new ammonia and urea/UAN plants at our Donaldsonville, Louisiana complex and new ammonia and urea plants at our Port Neal, Iowa complex.
A portion of the capacity expansion project costs are euro-denominated.
In order to manage our exposure to changes in the euro to U. S.  dollar currency exchange rates, we have hedged our projected euro-denominated payments through the third quarter of 2016 using foreign currency forward contracts.
As of December 31, 2015 and 2014, the notional amount of our open foreign currency derivatives was €89.0 million and €209.0 million, respectively.
None of these open foreign currency derivatives were designated as hedging instruments for accounting purposes.
During the year ended December 31, 2014, we reclassified a pre-tax gain of $2.8 million from accumulated other comprehensive income (AOCI) to income as a result of the discontinuance of certain foreign currency derivatives, which were originally designated as cash flow hedges.
No reclassification from AOCI to income occurred in 2015 or 2013.
As of December 31, 2015 and December 31, 2014, AOCI includes $7.4 million of pre-tax gains related to the foreign currency derivatives that were originally designated as cash flow hedges.
The hedges were de-designated as of December 31, 2013, and the remaining balance in AOCI will be reclassified into income over the depreciable lives of the property, plant and equipment associated with the capacity expansion projects.
We expect that the amounts to be reclassified within the next twelve months will be insignificant.
See Note 18¡ªStockholders' Equity, for further information.
The effect of derivatives in our consolidated statements of operations is shown in the tables below:
## Table 0 ##
## Table 1 ##
(1) For foreign exchange contracts designated as cash flow hedges, the amount reported as loss recognized in income in 2013 represents the amount excluded from hedge effectiveness.
CF INDUSTRIES HOLDINGS, INC.  127 19.
Stock-Based Compensation 2014 Equity and Incentive Plan On May 14, 2014, our shareholders approved the CF Industries Holdings, Inc.  2014 Equity and Incentive Plan (the Plan) which replaced the CF Industries Holdings, Inc.  2009 Equity and Incentive Plan.
Under the Plan, we may grant incentive stock options, nonqualified stock options, stock appreciation rights, restricted stock, restricted stock units, performance awards (payable in cash or stock) and other stock-based awards to our officers, employees, consultants and independent contractors (including non-employee directors).
The purpose of the Plan is to provide an incentive for our employees, officers, consultants and non-employee directors that is aligned with the interests of our stockholders.
Five-for-One Stock Split On June 17, 2015, stockholders of record as of the close of business on June 1, 2015 (Record Date) received four additional shares of common stock for each share of common stock held on the Record Date in the form of a stock dividend (five-for-one stock split).
Share and per share amounts have been retroactively restated to reflect the five-for-one stock split.
Shares reserved under the Company's equity and incentive plans were adjusted to reflect the five-for-one stock split.
Share Reserve and Individual Award Limits The maximum number of shares reserved for the grant of awards under the Plan is the sum of (i) 13.9 million and (ii) the number of shares subject to outstanding awards under our predecessor plans to the extent such awards terminate or expire without delivery of shares.
For purposes of determining the number of shares of stock available for grant under the Plan, each option or stock appreciation right is counted against the reserve as one share.
Each share of stock granted, other than an option or a stock appreciation right, is counted against the reserve as 1.61 shares.
If any outstanding award expires or is settled in cash, any unissued shares subject to the award are again available for grant under the Plan.
Shares tendered in payment of the exercise price of an option and shares withheld by the Company or otherwise received by the Company to satisfy tax withholding obligations are not available for future grant under the Plan.
As of December 31, 2015, we had 13.1 million shares available for future awards under the Plan.
The Plan provides that no more than 5.0 million underlying shares may be granted to a participant in any one calendar year.
Stock Options Under the Plan and our predecessor plans, we granted to plan participants nonqualified stock options to purchase shares of our common stock.
The exercise price of these options is equal to the market price of our common stock on the date of grant.
The contractual life of each option is ten years and generally one-third of the options vest on each of the first three anniversaries of the date of grant.
The fair value of each stock option award is estimated using the Black-Scholes option valuation model.
Key assumptions used and resulting grant date fair values are shown in the following table.
## Table 2 ##
(1) The grant date fair values used to calculate the weighted-average grant date fair value have been retroactively restated for all prior periods presented to reflect the five-for-one stock split.
The expected volatility of our stock options is based on the combination of the historical volatility of our common stock and implied volatilities of exchange traded options on our common stock.
The expected term of options is estimated based on our historical exercise experience, post-vesting employment termination behavior and the contractual term.
The risk-free interest rate is based on the U. S.  Treasury Strip yield curve in effect at the time of grant for the expected term of the options.
CF INDUSTRIES HOLDINGS, INC.  54 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; and Medicine Hat, Alberta nitrogen complexes.
The following table presents summary operating data for our granular urea segment
## Table 3 ##
(1) Granular urea represents 46% nitrogen content.
Nutrient tons represent the tons of nitrogen within the product tons.
Year Ended December 31, 2015 Compared to Year Ended December 31, 2014 Net Sales.
Net sales in the granular urea segment decreased by $126.5 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 primarily due to the excess global supply availability weighing on global nitrogen fertilizer selling prices.
Granular urea exports from China were at a record high in 2015 and Russian exports have increased significantly while global capacity additions in 2015 further contributed to the excess global supply.
Our sales volume 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 of 2015.
Cost of Sales.
Cost of sales per ton in our granular urea segment averaged $191 per ton in 2015, a 9% decrease from 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.
Year Ended December 31, 2014 Compared to Year Ended December 31, 2013 Net Sales.
Net sales in the granular urea segment decreased by $10.1 million, or 1%, for 2014 compared to 2013 due primarily to a 2% decrease in sales volume, partially offset by a 1% increase in average selling prices.
The comparability of the granular urea segment net sales was impacted by the CFL selling price modifications in 2013.
On an as adjusted basis, net sales decreased by $36.4 million, or 4%, and average selling prices decreased 2%.
Volumes were lower mainly due to our decision to reduce export volume as compared to 2013 due to anticipated robust domestic demand.
The poor fall 2014 ammonia season combined with a tight ammonia supply contributed to increased demand at the end of 2014 and expectations for a strong 2015 spring season.
Cost of Sales.
Cost of sales per ton in our granular urea segment averaged $210 per ton in 2014, a 28% increase over the $164 per ton in 2013 due primarily to increased natural gas costs which increased 16%, plus the impact of mark-to-market on natural gas derivatives which increased granular urea segment gas costs by $33.0 million compared to 2013.
NOTES TO CONSOLIDATED FINANCIAL STATEMENTS—(Continued) UCS.
As of May 31, 2009, $55.0 million of the purchase price was held in escrow (the “escrow account”).
Prior to our acquisition of UCS, the former parent company of UCS pledged the company’s stock as collateral for a third party loan (“the loan”) that matures on September 24, 2009.
Upon repayment of this loan, the stock will be released to us and $35.0 million of the purchase price will be released to the seller.
The remaining $20.0 million will remain in escrow until January 1, 2013, to satisfy any liabilities discovered post-closing that existed at the purchase date.
The purpose of this acquisition was to establish an acquiring presence in the Russian market and a foundation for other direct acquiring opportunities in Central and Eastern Europe.
The purchase price was determined by analyzing the historical and prospective financial statements and applying relevant purchase price multiples.
This business acquisition was not significant to our consolidated financial statements and accordingly, we have not provided pro forma information relating to this acquisition.
Upon acquisition of UCS Global Payments assumed an indirect guarantee of the loan.
In the event of a default by the third-party debtor, we would be required to transfer all of the shares of UCS to the trustee or pay the amount outstanding under the loan.
At May 31, 2009 the maximum potential amount of future payments under the guarantee was $44.1 million which represents the total outstanding under the loan, consisting of $21.8 million due and paid on June 24, 2009 and $22.3 million due on September 24, 2009.
Should the third-party debtor default on the final payment, Global Payments would pay the total amount outstanding and seek to be reimbursed for any payments made from the $55 million held in the escrow account.
We did not record an obligation for this guarantee because we determined that the fair value of the guarantee is de minimis.
The following table summarizes the preliminary purchase price allocation (in thousands):

Tables referenced above, in order (Table 0 first):
<table><tr><td></td><td colspan="3" rowspan="2"Gain (loss) recognized in OCI Year ended December 31,></td><td colspan="4">Gain (loss) reclassified from AOCI into income</td></tr><tr><td></td><td></td><td colspan="3">Year ended December 31,</td></tr><tr><td>Derivatives designatedas cash flow hedges</td><td>2015</td><td>2014</td><td>2013</td><td>Location</td><td>2015</td><td>2014</td><td>2013</td></tr><tr><td></td><td colspan="3">(in millions)</td><td></td><td colspan="3">(in millions)</td></tr><tr><td>Foreign exchange contracts</td><td>$—</td><td>$—</td><td>$3.0</td><td>Other operating—net</td><td>$—</td><td>$2.8</td><td>$—</td></tr></table>
<table><tr><td></td><td colspan="4">Gain (loss) recognized in income</td></tr><tr><td></td><td></td><td colspan="3">Year ended December 31,</td></tr><tr><td></td><td>Location</td><td>2015</td><td>2014</td><td>2013</td></tr><tr><td></td><td></td><td colspan="3">(in millions)</td></tr><tr><td>Foreign exchange contracts</td><td>Other operating—net<sup>-1</sup></td><td>$—</td><td>$—</td><td>$-1.8</td></tr></table>
<table><tr><td></td><td>2015</td><td>2014</td><td>2013</td></tr><tr><td>Weighted-average assumptions:</td><td></td><td></td><td></td></tr><tr><td>Expected volatility</td><td>31%</td><td>33%</td><td>35%</td></tr><tr><td>Expected term of stock options</td><td>4.3 Years</td><td>4.3 Years</td><td>4.4 Years</td></tr><tr><td>Risk-free interest rate</td><td>1.5%</td><td>1.3%</td><td>1.4%</td></tr><tr><td>Expected dividend yield</td><td>1.9%</td><td>1.6%</td><td>0.8%</td></tr><tr><td>Weighted-average grant date fair value<sup>-1</sup></td><td>$13.99</td><td>$12.77</td><td>$10.76</td></tr></table>
<table><tr><td></td><td colspan="7">Twelve months ended December 31,</td></tr><tr><td></td><td>2015</td><td>2014</td><td>2013</td><td colspan="2">2015 v. 2014</td><td colspan="2">2014 v. 2013</td></tr><tr><td></td><td colspan="7">(in millions, except as noted)</td></tr><tr><td>Net sales</td><td>$788.0</td><td>$914.5</td><td>$924.6</td><td>$-126.5</td><td>-14%</td><td>$-10.1</td><td>-1%</td></tr><tr><td>Cost of sales</td><td>469.5</td><td>516.6</td><td>410.1</td><td>-47.1</td><td>-9%</td><td>106.5</td><td>26%</td></tr><tr><td>Gross margin</td><td>$318.5</td><td>$397.9</td><td>$514.5</td><td>$-79.4</td><td>-20%</td><td>$-116.6</td><td>-23%</td></tr><tr><td>Gross margin percentage</td><td>40.4%</td><td>43.5%</td><td>55.6%</td><td>-3.1%</td><td></td><td>-12.1%</td><td></td></tr><tr><td>Sales volume by product tons (000s)</td><td>2,460</td><td>2,459</td><td>2,506</td><td>1</td><td>—%</td><td>-47</td><td>-2%</td></tr><tr><td>Sales volume by nutrient tons (000s)<sup>(1)</sup></td><td>1,132</td><td>1,131</td><td>1,153</td><td>1</td><td>—%</td><td>-22</td><td>-2%</td></tr><tr><td>Average selling price per product ton</td><td>$320</td><td>$372</td><td>$369</td><td>$-52</td><td>-14%</td><td>$3</td><td>1%</td></tr><tr><td>Average selling price per nutrient ton<sup>-1</sup></td><td>$696</td><td>$809</td><td>$802</td><td>$-113</td><td>-14%</td><td>$7</td><td>1%</td></tr><tr><td>Gross margin per product ton</td><td>$129</td><td>$162</td><td>$205</td><td>$-33</td><td>-20%</td><td>$-43</td><td>-21%</td></tr><tr><td>Gross margin per nutrient ton<sup>-1</sup></td><td>$281</td><td>$352</td><td>$446</td><td>$-71</td><td>-20%</td><td>$-94</td><td>-21%</td></tr><tr><td>Depreciation and amortization</td><td>$50.5</td><td>$37.5</td><td>$37.4</td><td>$13.0</td><td>35%</td><td>$0.1</td><td>—%</td></tr></table>

Question: In the year with lowest amount of Net sales, what's the increasing rate of Cost of sales?
Answer: -0.09117
Reasoning program: subtract(469.5,516.6), divide(#0,516.6)