It's a comparison that we certainly could do, but I would want to emphasize that it's not particularly of interest to us as an institute to compare materials. One form of the engagement that we get from industry is that industries are looking to make improvement within their sectors. The Cement Association is one example of an organization that has done that.
The point I'd like to make is that all materials have impact. We build with all materials. They're all critical to construction. What is more interesting to us is how we encourage improvements across all those sectors, so that we overall have an improvement and a reduction in environmental impacts.