Futurist and singularitarian Ray Kurzweil recently told PBS: "One of my primary theses is that information technologies grow exponentially in capability and power and bandwidth and so on. If you buy an iPhone today, it's twice as good as two years ago for half that cost. That is happening with solar energy—it is doubling every two years. And it didn't start two years ago, it started 20 years ago. Every two years we have twice as much solar energy in the world. Today, solar is still more expensive than fossil fuels, and in most situations it still needs subsidies or special circumstances, but the costs are coming down rapidly—we are only a few years away from parity."