Like any growth story, alternative energy is difficult to analyze unless you can measure it.

So it's worth noting how hard people are trying to track this business with new indices. There are now at least seven clean energy indices including the Cleantech Index, the German Börse’s DAXglobal Alternative Energy Index, the WilderHill Clean Energy Global Innovation Index, and the Ardour Global Alternative Energy Index (see Clean Capital, Tracking Clean Energy Globally, and Cleantech Index Soup).

And now ETFs are being created to mirror them.

I daresay we'll get a few more indices but after a few years, one will be established as the definitive index. And my guess is that it will be global.