While many media companies have rushed to build apps for iPads and Android tablets, they say their current inability to sell standard subscriptions through iTunes, a shortage of data about app buyers and tough business terms are keeping them from investing more in the effort.

WSJ: Google Digital Newsstand Aims to Muscle In on Apple

Hence, the current business model boasts a continuing upward trend of improving margins, improving conversion to paid subscriptions, and improved profitability of each subscriber.

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