"While the proportion of the population using mobile phones has stabilised in most developed-world markets at around 80-85%, the trend among many users for buying second or even third subscriptions shows no sign of slowing," comments Devine Kofiloto, Principal Analyst at Informa Telecoms and Media. "Operators in these markets are actively encouraging the practice, selling prepaid SIM cards with US$5 or US$10 of preloaded credit in order to boost their subscription numbers, cut acquisition costs and promote value-added services," continued Kofiloto.

Multiple SIM card ownership may be having a negative impact on operator ARPU but it continues to help increase overall usage levels. This in turn is helping operators in developed markets to stabilise revenues in the face of competitive pressure on tariffs. The phenomenon of multiple SIM card ownership is not restricted to the developed world but is also common in developing markets such as China and Nigeria.

Informa Telecoms and Media forecasts that by the end of 2006 the number of countries with mobile penetration over 100% will reach 40. Additions to the list will include Russia, the third largest mobile market in the world. Russia added more than 50 million mobile subscriptions in 2005 but growth rates in the country are now slowing as penetration in Russia's regional markets climbs nearer to saturation point.