Proportion of research output as data or publication?

My colleague Graham Pryor asks in an email:

"Chris - I have been looking for evidence of the proportion of UK research output that can be categorised as scholarly publications and that which is in the form of data. I have found nothing. It is quite possible that no-one has ever tried to work this out. However, on the off-chance, is this a figure (even an estimate) that you might have come across?"

I think this is a great question, even an "Emperor's New Clothes" question. "Everyone knows" that the data proportion has been increasing, but I know of no estimates of the proportions.Does anyone else know of such estimates? If not, does anyone have any idea how to set about making such an estimate? A very clear definition of data would be needed, to include externally usable data perhaps, rather than raw telemetry...(Apologies for the gap in posting, I have been sequestered on a Greek island for a couple of weeks, and not thinking of you at all!)