The big idea

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Economist Hernando de Soto is a man with a big idea. He is President of the ILD think-tank in Peru and he advises a string of world leaders. He wants to persuade governments to give land and property rights to poor people, to give them a legal identity. The theory is, they can then borrow against these assets which helps to build businesses and economies. He told Lesley Curwen that the first step is identifying how many 'extra-legal' people live in a country, and establishing who they are. Plus, the BBC's environment correspondent David Shukman reports from Kenya on the economic value of its natural assets - its forests. And our Washington commentator, James Srodes wonders whether illegal immigration might actually provide an economic boost for America.