decreased production volume as final aircraft deliveries were completed during the second quarter of 2012 and $50 million from the favorable resolution of a contractual matter during the second quarter of 2012; and about $270 million for various other programs (primarily sustainment activities) due to decreased volume.
The decreases were partially offset by higher net sales of about $295 million for F-35 production contracts due to increased production volume and risk retirements; approximately $245 million for the C-5 program due to increased aircraft deliveries (six aircraft delivered in 2013 compared to four in 2012) and other modernization activities; and about $70 million for the F-35 development contract due to increased volume.
Aeronautics’ operating profit for 2013 decreased $87 million, or 5%, compared to 2012.
The decrease was primarily attributable to lower operating profit of about $85 million for the F-22 program, which includes approximately $50 million from the favorable resolution of a contractual matter in the second quarter of 2012 and about $35 million due to decreased risk retirements and production volume; approximately $70 million for the C-130 program due to lower risk retirements and fewer deliveries partially offset by increased sustainment activities; about $65 million for the C-5 program due to the inception-to-date effect of reducing the profit booking rate in the third quarter of 2013 and lower risk retirements; approximately $35 million for the F-16 program due to fewer aircraft deliveries partially offset by increased sustainment activity and aircraft configuration mix.
The decreases were partially offset by higher operating profit of approximately $180 million for F-35 production contracts due to increased risk retirements and volume.
Operating profit was comparable for the F-35 development contract and included adjustments of approximately $85 million to reflect the inception-to-date impacts of the downward revisions to the profit booking rate in both 2013 and 2012.
Adjustments not related to volume, including net profit booking rate adjustments and other matters, were approximately $75 million lower for 2013 compared to 2012.
Backlog Backlog decreased slightly in 2014 compared to 2013 primarily due to lower orders on F-16 and F-22 programs.
Backlog decreased in 2013 compared to 2012 mainly due to lower orders on F-16, C-5 and C-130 programs, partially offset by higher orders on the F-35 program.
Trends We expect Aeronautics’ 2015 net sales to be comparable or slightly behind 2014 due to a decline in F-16 deliveries as well as a decline in F-35 development activity, partially offset by an increase in production contracts.
Operating profit is also expected to decrease in the low single digit range, due primarily to contract mix, resulting in a slight decrease in operating margins between years.
Information Systems & Global Solutions Our IS&GS business segment provides advanced technology systems and expertise, integrated information technology solutions and management services across a broad spectrum of applications for civil, defense, intelligence and other government customers.
IS&GS has a portfolio of many smaller contracts as compared to our other business segments.
IS&GS has been impacted by the continued downturn in certain federal agencies’ information technology budgets and increased re-competition on existing contracts coupled with the fragmentation of large contracts into multiple smaller contracts that are awarded primarily on the basis of price.
IS&GS’ operating results included the following (in millions):
## Table 0 ##
2014 compared to 2013 IS&GS’ net sales decreased $579 million, or 7%, for 2014 compared to 2013.
The decrease was primarily attributable to lower net sales of about $645 million for 2014 due to the wind-down or completion of certain programs, driven by reductions in direct warfighter support (including JIEDDO and PTDS) and defense budgets tied to command and control programs; and approximately $490 million for 2014 due to a decline in volume for various ongoing programs, which reflects lower funding levels and programs impacted by in-theater force reductions.
The decreases were partially offset by higher net sales of about $550 million for 2014 due to the start-up of new programs, growth in recently awarded programs and integration of recently acquired companies.
asset-backed securities collateralized by sub-prime mortgages, $0.6 billion were other asset-backed securities and $0.5 billion were municipal bonds, which are included within the U. S.  Government line of the fixed maturity securities composition table above.
Management estimates that 63% of the asset-backed securities collateralized by sub-prime mortgages, 79% of the other asset-backed securities, and virtually all of the municipal bonds would have investment grade credit ratings giving no effect to the support of these securities by guarantees from monoline bond insurers.
As of December 31, 2007, the bond insurance is provided by five insurance companies, with no company representing more than 29% of the overall amortized cost of the securities supported by bond insurance attributable to the Financial Services Businesses.
As of December 31, 2007, on an amortized cost basis, $1.4 billion ($1.3 billion fair value), or 3%, of fixed maturity investments attributable to the Closed Block Business were supported by guarantees from monoline bond insurers.
All of these investments had AAA credit ratings as of December 31, 2007, reflecting the credit quality of the monoline bond insurer.
Management estimates, taking into account the structure and credit quality of the underlying investments and giving no effect to the support of these securities by guarantees from monoline bond insurers, that 81% of the $1.4 billion total (based upon amortized cost) would have investment grade credit ratings.
Based on amortized cost, $1.1 billion of the $1.4 billion of securities supported by bond insurance were asset-backed securities collateralized by sub-prime mortgages, $0.2 billion were other asset-backed securities, and $0.1 billion were municipal bonds, which are included within the U. S.  Government line of the fixed maturity securities composition table above.
Management estimates that 78% of the asset-backed securities collateralized by sub-prime mortgages, 85% of the other asset-backed securities, and all of the municipal bonds would have investment grade credit ratings giving no effect to the support of these securities by guarantees from monoline bond insurers.
As of December 31, 2007, the bond insurance is provided by five insurance companies, with no company representing more than 35% of the overall amortized cost of the securities supported by bond insurance attributable to the Closed Block Business.
The amortized cost of our public and private below investment grade fixed maturities attributable to the Financial Services Businesses totaled $7.5 billion, or 7%, of the total fixed maturities as of December 31, 2007 and $7.1 billion, or 6%, of the total fixed maturities as of December 31, 2006.
Below investment grade fixed maturities represented 12% and 11% of the gross unrealized losses attributable to the Financial Services Businesses as of December 31, 2007 and December 31, 2006, respectively.
The amortized cost of our public and private below investment grade fixed maturities attributable to the Closed Block Business totaled $5.7 billion, or 12%, of the total fixed maturities as of December 31, 2007 and $6.2 billion, or 13%, of the total fixed maturities as of December 31, 2006.
Below investment grade fixed maturities represented 18% of the gross unrealized losses attributable to the Closed Block Business as of December 31, 2007, compared to 16% of gross unrealized losses as of December 31, 2006.
Public Fixed Maturities—Credit Quality The following table sets forth our public fixed maturity portfolios by NAIC rating attributable to the Financial Services Businesses as of the dates indicated.
## Table 1 ##
(1) Reflects equivalent ratings for investments of the international insurance operations that are not rated by U. S.  insurance regulatory authorities.
(2) Includes, as of December 31, 2007 and December 31, 2006, respectively, 14 securities with amortized cost of $49 million (fair value, $46 million) and 10 securities with amortized cost of $50 million (fair value, $51 million) that have been categorized based on expected NAIC designations pending receipt of SVO ratings.
(3) Includes $25 million of gross unrealized gains and $39 million gross unrealized losses as of December 31, 2007, compared to $22 million of gross unrealized gains and $47 million of gross unrealized losses as of December 31, 2006 on securities classified as held to maturity that are not reflected in other comprehensive income.
UNITED PARCEL SERVICE, INC.  AND SUBSIDIARIES MANAGEMENT'S DISCUSSION AND ANALYSIS OF FINANCIAL CONDITION AND RESULTS OF OPERATIONS 30 Revenue per piece for ground and air products was positively impacted by a base rate increase on December 28, 2015.
UPS Ground rates and accessorial charges increased an average net 4.9%, while UPS Air services and accessorial charges increased an average net 5.2%.
The surcharge increased for Over Maximum Packages and the index tables for the Ground and Air fuel surcharges were adjusted effective November 2, 2015.
A charge for UPS’s Third-Party Billing Service was implemented, effective January 4, 2016.
Additionally, the dimensions of ground packages incurring the UPS Additional Handling charge were changed effective June 6, 2016.2015 compared to 2014 Overall revenue per piece increased 0.3% in 2015, and was impacted by changes in base rates, customer and product mix and fuel surcharge rates.
Revenue per piece for our ground and air products was positively impacted by an increase in base rates which took effect on December 29, 2014 and an increase in surcharge rates that took effect November 2, 2015.
We implemented an average 4.9% net increase in base and accessorial rates on UPS Next Day Air, UPS 2nd Day Air, UPS 3 Day Select and UPS Ground.
Additionally, a pricing change involving the application of dimensional weight pricing to all UPS Ground services took effect on December 29, 2014.
On November 2, 2015, the surcharge increased for Over Maximum Packages and the indices for Ground, Air and International fuel surcharges were adjusted.
Revenue per piece decreased for our Next Day Air and deferred air products in 2015, as lower fuel surcharge rates more than offset the positive impact of the base rate increase.
Product mix adversely impacted Next Day Air and deferred revenue per piece, as we experienced relatively stronger growth in our lighter-weight business-to-consumer shipments, which have lower average yields than our heavier-weight commercial shipments.
Customer mix also adversely impacted Next Day Air and deferred revenue per piece, due to faster volume growth among our larger customers, which typically have a lower average yield than our small and middle-market customers.
Ground revenue per piece increased in 2015, primarily due to the base rate increase, the dimensional weight pricing change and product mix.
Additionally, the revenue per piece for our traditional ground residential products was positively impacted by our decision not to pursue certain lower-yielding customer contract renewals.
These factors were partially offset by declines in fuel surcharge rates as well as changes in customer mix, as we experienced faster volume growth among our larger customers.
Fuel Surcharges UPS applies a fuel surcharge on our domestic air and ground services.
The air fuel surcharge is based on the U. S.  Department of Energy’s (“DOE”) Gulf Coast spot price for a gallon of kerosene-type jet fuel, while the ground fuel surcharge is based on the DOE’s On-Highway Diesel Fuel Price.
Based on published rates, the average fuel surcharge rates for domestic air and ground products were as follows:
## Table 2 ##
Total domestic fuel surcharge revenue decreased by $219 million in 2016 as a result of lower fuel surcharge rates caused by declining jet and diesel fuel prices, partially offset by the overall increase in package volume for the period.
In 2015, total fuel surcharge revenue declined by $843 million as a result of lower fuel surcharge rates caused by declining jet and diesel fuel prices; however, the impact of lower fuel prices was partially mitigated by changes to the fuel surcharge indices, as well as the overall increase in package volume for the period.

<table><tr><td></td><td>2014</td><td>2013</td><td>2012</td></tr><tr><td>Net sales</td><td>$7,788</td><td>$8,367</td><td>$8,846</td></tr><tr><td>Operating profit</td><td>699</td><td>759</td><td>808</td></tr><tr><td>Operating margins</td><td>9.0%</td><td>9.1%</td><td>9.1%</td></tr><tr><td>Backlog at year-end</td><td>$8,700</td><td>$8,300</td><td>$8,700</td></tr></table>
<table><tr><td> -1 (2)</td><td></td><td colspan="4"> December 31, 2007</td><td colspan="4"> December 31, 2006</td></tr><tr><td> NAIC Designation</td><td> Rating Agency Equivalent</td><td> Amortized Cost</td><td> Gross Unrealized Gains-3</td><td> Gross Unrealized Losses-3</td><td> Fair Value</td><td> Amortized Cost</td><td> Gross Unrealized Gains-3</td><td> Gross Unrealized Losses-3</td><td> Fair Value</td></tr><tr><td></td><td></td><td colspan="8"> (in millions)</td></tr><tr><td>1</td><td>Aaa, Aa, A</td><td>$74,678</td><td>$2,036</td><td>$1,184</td><td>$75,530</td><td>$75,796</td><td>$1,787</td><td>$322</td><td>$77,261</td></tr><tr><td>2</td><td>Baa</td><td>13,573</td><td>490</td><td>351</td><td>13,712</td><td>13,328</td><td>580</td><td>137</td><td>13,771</td></tr><tr><td></td><td>Subtotal Investment Grade</td><td>88,251</td><td>2,526</td><td>1,535</td><td>89,242</td><td>89,124</td><td>2,367</td><td>459</td><td>91,032</td></tr><tr><td>3</td><td>Ba</td><td>2,830</td><td>68</td><td>102</td><td>2,796</td><td>2,692</td><td>109</td><td>22</td><td>2,779</td></tr><tr><td>4</td><td>B</td><td>1,681</td><td>38</td><td>82</td><td>1,637</td><td>1,746</td><td>93</td><td>23</td><td>1,816</td></tr><tr><td>5</td><td>C and lower</td><td>115</td><td>5</td><td>6</td><td>114</td><td>115</td><td>8</td><td>2</td><td>121</td></tr><tr><td>6</td><td>In or near default</td><td>34</td><td>5</td><td>1</td><td>38</td><td>48</td><td>7</td><td>1</td><td>54</td></tr><tr><td></td><td>Subtotal Below Investment Grade</td><td>4,660</td><td>116</td><td>191</td><td>4,585</td><td>4,601</td><td>217</td><td>48</td><td>4,770</td></tr><tr><td></td><td>Total Public Fixed Maturities</td><td>$92,911</td><td>$2,642</td><td>$1,726</td><td>$93,827</td><td>$93,725</td><td>$2,584</td><td>$507</td><td>$95,802</td></tr></table>
<table><tr><td></td><td colspan="3">Year Ended December 31,</td><td colspan="2">% Point Change</td></tr><tr><td></td><td>2016</td><td>2015</td><td>2014</td><td>2016/ 2015</td><td>2015/ 2014</td></tr><tr><td>Next Day Air / Deferred</td><td>3.6%</td><td>4.8%</td><td>10.2%</td><td>-1.2%</td><td>-5.4%</td></tr><tr><td>Ground</td><td>4.9%</td><td>5.5%</td><td>7.1%</td><td>-0.6%</td><td>-1.6%</td></tr></table>

Question: Which year is the Fair Value for Rating Agency Equivalent Ba on December 31 the highest?
Answer: 2007