Based on reports from six Indonesian telecommunication operators, a total of 333.6 million active mobile numbers were in use at the end of Q1-2016, up a modest 1 percent from the preceding quarter. Given that the total population of Indonesia numbers around 255 million individuals, while the adult population is estimated at 150 million, it implies that many Indonesians use two or more mobile numbers.

Kristiono, Chairman of the Indonesia Telecommunication Society (a non-profit telecommunications lobby group), said those Indonesians who do not have a mobile number yet are either young children or the poor who lack enough purchasing power to buy a mobile device. According to the latest data from Statistics Indonesia (BPS), there were 28 million Indonesians - or 10.9 percent of the Indonesian population - living below the poverty line in March 2016.

Besides waiting for younger generations to become mobile subscribers, Indonesia's telecommunication operators should also try to encourage existing mobile phone users to use more data services (for example mobile chat applications) or offer more mobile content and apps in order to boost earnings.

Read more: Internet & Smartphone Penetration in Indonesia Estimated to Grow Strongly

The four firms that control nearly 90 percent of Indonesia’s mobile phone market are Telekomunikasi Indonesia (Telkom), Indosat Ooredoo, Hutchison 3 Indonesia and XL Axiata. Through its subsidiary Telekomunikasi Seluler, Telkom is the clear market leader. The company had 153.6 million subscribers by the end of March 2016, more than double Indosat Ooredoo's 69.8 million subscribers. Hutchison 3 Indonesia has 55.5 million subscribers, while XL Axiata has 42.5 million subscribers.