Counting the cost of Mexico's drug violence

Five years ago, Mexico President Felipe Calderon launched a war on drug cartels.

Since then at least 40,000 people have been killed in drug-related crimes, according to official figures.

But the government stopped updating its total figure at the end of 2010, making it difficult to track progress in 2011.

Political scientist Eduardo Guerrero puts the total at 47,500, if deaths reported in the newspapers this year are included. Others believe the government has been too narrow in its definitions and the total could be approaching 60,000.

Where do the cartels get their guns and their money from? And which Mexican states are the worst affected?