Smartphone manufacturers may be seeing their sales growth slow in established western markets, but the companies providing mobile data access on the those devices are still seeing their revenues soar.

Market research firm ABI Research today released a report estimating that mobile internet service revenue rose over 23% worldwide in 2013, up to nearly $300 billion. Smartphones are becoming more ubiquitous, making up 27.5% of consumer mobile data subscriptions last year – a 6.6% increase from that seen in 2012. Overall, mobile data broadband subscriptions rose nearly 29% in 2013.

“The region that will contribute the most to the increase in mobile Internet service revenue is North America, despite the maturity of the North American market and that only 5.5% of global cellular subscriptions are based there,” said Ying Kang Tan, a research associate at ABI. “Higher smartphone penetration and increased mobile data consumption have helped the region to buck the declining ARPU trend. We expect ARPU in the region to rise in 2014 before declining again due to competition and lower revenue generating connections subscribing to mobile broadband.”

As potential new mobile customers begin to dry up in the U.S., mobile providers in the country are now scrambling to find new sources of revenue growth. T-Mobile is hoping to buy customers away from other carriers with its consumer-friendly “Uncarrier” initiatives. AT&T will soon begin charging consumers and content providers for data flowing on its 4G network through its “Sponsored Data” program, but only if the company manages to placate the FCC and net neutrality advocates.