I must have missed the explanation on the chart showing Mobile Penetration by country. Can someone explain how a country like Vietnam has 173% penetration? Does a penetration greater than 100% mean many people have two cell phones?
I've heard (but can't find a link ATM) that it's not uncommon for people in developing countries have multiple phones or multiple SIM cards and will call on one or the other depending on that provider's current rates.
Not only that, but I know also many freelancers that have one personal phone/sim and one business phone/sim.
In Vietnam, and in many countries in the developing world, mobile phone users have multiple sim cards to take advantage of competitive rates and to call friends/family on network. Calls to mobiles using the same operator are often significantly cheaper. Many phones (smartphones included) released in the developing world even have multi-sim card ports.
One person can have 2-3 phones with different SIM's.