Green roofs installations are down, what does it mean?

For the first time since they started keeping records, Green Roofs for Healthy Cities (GRHC) reported in 2014, among corporate members in North America, green roof installations were down 10%. What does it mean?
GRHC offers a few possible explanations as to why, after years of posting strong numbers according to their methodology, the industry suffered what appears to be a downswing:

-A few key federal subsidies ended last year;
-Private sector companies may be sitting on capital rather than investing them in building improvements.

I believe both of these could have contributed to the lower numbers. We should also remember a few other things:

-Not all firms in the industry are (or are required to be) GRHC members;
-Not all firms are willing (or have the time) to participate in the survey;

So what we've had in the past, and will continue to have, are data from a fraction of the projects. To know how many roofs were actually done, I would think more exhaustive research techniques might be necessary. Contacting medium suppliers, regardless of their affiliation, to see how many projects they are aware of. Plant suppliers are well. 

-And while we are chatting about publications, here are a couple from the academic realm. The first attempts to quantify how well mature green roofs retain water. Can they green roofs really be used for flood mitigation? The second focuses on a specific type of turfgrass used on green roofs and asks the question, how do you best take care of it?