Africa’s fast-growing mobile phone subscription rate is expected to slow sharply in the next five years, a development that has surprised some stakeholders closest to the industry, Reuters reports in eNCA.

African mobile subscriptions grew 13 percent from 2010 to 2015, and they’ll continue to grow, but slower — at an expected rate of 6 percent from 2015 to 2020 — according to a new report by global industry body GSMA.

That 6-percent growth will likely add 135 million subscribers, ITNewsAfrica reports.

The report says the slowdown will be partly due to lack of commercial logic in setting up network coverage in some rural areas, where more than half the population lives, Reuters reports.

The slowing subscriber growth underscores the existence of significant barriers to the take-up of mobile services, according to ITNewsAfrica. In addition to a lack of business confidence in rural areas, these include cost, coverage, income levels and technical literacy.

Sub-Saharan Africa bypassed Latin America for unique subscribers in 2014, becoming the world’s third-largest growth region after Asia Pacific and Europe. It now accounts for 10 percent of the global subscriber base, ITNewsAfrica reports.

So what’s the problem?

It’s not economically viable for mobile phone companies to deploy their networks in some areas — especially remote, rural communities — because of low spending power of people living there, said Mortimer Hope, GSMA’s Africa director.

“I am bit surprised by this development,” Hope told Reuters. “I expected strong growth to continue because the penetration rate in Africa is still well below 100 percent.”

Expect more mergers and acquisitions as competition heats up and subscription rates go down in African mobile markets, Hope said.

“Smaller players don’t have the economies of scale to drive their prices down and compete for long periods, so you’ll probably see some consolidation in the market,” he said.

Recent M&A activity includes United Arab Emirates’ Etisalat selling Zantel, its struggling Tanzanian mobile phone business, to Sweden’s Millicom in June, Reuters reports.

South Africa’s Vodacom bought fixed-line operator Neotel, which struggled to compete against larger rival Telkom.

By 2020, more than 500 million people — about half the African population — will have subscribed to a mobile service compared with the global average of almost 60 percent, according to the GSMA report.

Mobile regulators and operators must act to reduce barriers to mobile uptake so the unconnected can get the benefits of mobile, ITNewsAfrica reports.

Between now and 2020, 40 percent of the new subscribers are expected to come from Ethiopia and Nigeria, two of the most populous countries in the region. Mobile penetration is now 23 percent in Ethiopia and 31 percent in Nigeria.

Other countries expected to have strong subscriber growth include Cameroon, Kenya, Mozambique, Tanzania and Uganda, ITNewsAfrica reports.