I found this statistic in the USA Today today. I thought it was interesting since we are green related.
Percentage increase in applications for U.S. trade-marks using these words and prefixes from 2007 to 2008 (with number of 2008 applications):
32% Green (3,240)
86% Eco- (1,730)
26% Enviro- (530)
30% Clean (260)
Source- Dechert LLP