The hidden black market fueling Mexico's cars — and its cartels

In Mexico, up to a third of all fuel sold may come from illegal sources - smuggled, stolen or adulterated. This black market fuels organized crime, drains billions from public coffers and puts ordinary people at risk. From Mexico City, The World's Tibisay Zea looks at how oil theft has evolved into one of Mexico's largest underground economies - and why it's so hard to stop.