Juniper on Wednesday released a new report indicating that revenues from mobile content, monetized through direct carrier billing, is poised to rise from $2 billion in 2012 to more than $13 billion by 2017.

But the report offers up less sunshine and fewer rainbows for operator storefronts and portals which now account for just 6% of content downloads worldwide. Google Play and Apple’s App Store comprise nearly 70% of this segment.

Juniper says the increasing popularity of OTT (Over The Top) stores had led to many operators closing their own storefronts.

The report – Mobile Content Business Models: OTT & Operator Strategy & Forecasts 2013-2017 – found that by offering carrier billing to third-party storefronts, operators could more than offset the continued decline in portal revenues.

According to Juniper, storefronts which have already integrated carrier billing solutions have seen a 5-6x increase in conversion rates compared with credit card billing, together with an uplift in average transaction values.

The new report from Juniper is available for purchase now.