While mobile phone usage has exploded across Africa over the last decade, transforming daily life and commerce for millions, it's a revolution that has left behind perhaps two thirds of its people.
In South Sudan, the world's newest state, it's a similar story. Less than a year old, the country already has five mobile operators, and its capital, Juba, is teeming with giant billboards advertising mobile phones, but go just a few kilometers beyond a handful of fast-growing towns, and cell phones become useless.
The average mobile phone user in Nigeria owns an average of 2.39 SIM cards. Globally, only Indonesia is higher, with an average of 2.62 SIM cards per user.
Even in Africa's biggest economy, South Africa, SIM numbers comfortably exceed the population, but given the number of people using multiple devices, actual population penetration is closer to 80 percent, says market leader Vodacom.
Average revenue per user is also low. It can vary between $1 and $10 per month, much lower than in developed markets such as the United States, which delivered ARPU of $51 in 2012 or Britain, $27.
African expansion has not been cheap for telcos. Over the past five years, mobile operators have spent a combined $16.5 billion on capital expenditure in the key markets of South Africa, Nigeria, Kenya, Senegal and Ghana, according to Wireless Intelligence.
Bharti has earmarked $1.5 billion for capex this year, while fourth-placed France Telecom is spending $9.3 billion between 2010 and 2015.
Spare cash is increasingly rare for debt-strapped European telecoms operators, which are cutting their dividends to cope with falling revenues and network upgrade costs in their home markets.