One possible explanation: there was a lot of hoopla around the addition of the gold-colored iPhone 5s as a very attractive addition in particular for Asian markets so this hypothesis may hold true. Keep in mind the gold-colored version is only available on the 5s, not the 5c.
Other major markets also had a very high ratio of the 5s vs. the 5c. In fact, the only country that didn’t have at least a 3 to 1 ratio of the 5s vs. the 5c was the United Kingdom. With the economy in the UK still in recovery, a slightly less strong affinity for the 5s could be the result of a more cost-conscious buyer. Subsidies also play less of a role in the UK’s phone market than in the US, making the upfront cost of phones higher for consumers. Globally the iPhone 5s represented 78% of all of the new iPhone 5s and 5c devices; 76% in the U.S. and 82% in the rest of the world.
Another reason why more iPhone 5s devices have been sold could be that 'hardcore' Apple users rushed out to purchase the latest and greatest iPhone device. Over the next few weeks the iPhone 5c could pick up momentum.
The United States accounted for 68% of all active iPhone 5s and iPhone 5c devices worldwide. Japan came in second with 13%.