currencies relative to the U.S. dollar, partially offset by a decline in net sales of iPad. iPhone growth resulted primarily from the successful introduction of iPhone 5s and 5c in the second half of calendar 2013 and the successful launch of iPhone 6 and 6 Plus in over 20 countries in Europe in September 2014. Mac growth was driven primarily by increased net sales and unit sales of MacBook Air, MacBook Pro and Mac Pro. 

Greater China experienced strong year-over-year increases in net sales during 2015 driven primarily by iPhone sales. 

The Greater China segment experienced year-over-year growth in net sales in 2014 that was significantly higher than the growth rate for the Company overall. Greater China growth was driven by higher unit sales and net sales of all major product categories, in addition to higher net sales of Services. Growth in net sales and unit sales of iPhone was especially strong, driven by the successful launch of iPhone 5s and 5c in Mainland China and Hong Kong in September 2013, the successful launch of iPhone 6 and 6 Plus in Hong Kong in September 2014, increased demand for the Company’s entry-priced iPhones and the addition of a significant new carrier in the second quarter of 2014. 

The year-over-year increase in Japan net sales during 2015 was driven primarily by growth in Services largely associated with strong App Store sales, partially offset by the effect of weakness in the Japanese yen relative to the U.S. dollar. 

In 2014 the Japan segment generated year-over-year increases in net sales and unit sales of every major product category and experienced growth in net sales of Services. The year-over-year growth in iPhone was driven by the successful launch of iPhone 5s and 5c in September 2013, the successful launch of iPhone 6 and 6 Plus in September 2014, increased demand for the Company’s entry-priced iPhones and the addition of a significant new carrier in the fourth quarter of 2013. These positive factors were partially offset by weakness in the Japanese Yen relative to the U.S. dollar. 

The year-over-year increase in Rest of Asia Pacific net sales during 2015 primarily reflects strong growth in net sales and unit sales of iPhone, partially offset by the effect of weakness in foreign currencies relative to the U.S. dollar and a decline in net sales and unit sales of iPad. 

Net sales in the Rest of Asia Pacific segment declined in 2014 compared to 2013 due to year-over-year reductions in net sales in all major product categories except Mac and reductions in unit sales of iPad. Net sales in 2014 were also negatively affected by the weakness in several foreign currencies relative to the U.S. dollar, including the Australian dollar. 

The year-over-year increase in the gross margin percentage in 2015 was driven primarily by a favorable shift in mix to products with higher margins and, to a lesser extent, by improved leverage on fixed costs from higher net sales. These positive factors were partially offset primarily by higher product cost structures and, to a lesser extent, by the effect of weakness in most foreign currencies relative to the U.S. dollar. 

The year-over-year increase in the gross margin