According to a report released in January 2006 by INDEC, mobile phone lines increased by 68.8% during 2005. Eleven million mobile phones were sold that year and, by then, these serviced three-quarters of the population over 14. A growing minority of users are children under 14, something that has raised concern and debate in Argentine society. A private study conducted by "Investigaciones Económicas Sectoriales" (IES), covering January–October 2006, found a 51.2% growth compared to the same period of 2005; by December 2007, the number of these units (40 million) exceeded Argentina's total population. Most of the phones (almost 90%) are imported from Brazil or Mexico. The monthly volume of calls made with these units (over 4.6 billion) more than doubles the number made on land lines; a further 6 billion text messages are sent, monthly.