Who wants to be a trillionaire? Well in developing countries, the clean technology market is estimated to be worth a staggering 6.4 trillion (with a T) dollars over the next decade. Michael Ehst, from the World Bank Group’s infoDev program, is excited about the massive growth of technologies that will help mitigate climate change. And he explains exactly how many zeros we’re talking about here. For more information visit http://www.infoDev.org/climate | 'My Favorite Number' is a series: When economists get excited, it’s usually for a good reason.