I spent a bit of time today running Peacekeeping.org's massive dataset through the hopper. My Stata coding was pretty brutish, but it did come up with the accompanying graph
pretty quickly. The dataset covers all UN 'chapter 6-and-a-half' missions from 1991 to the present, for all countries and presented in monthly totals. I've just reproduced the
relative Canadian contribution here.
In my puttering around the UN DPKO website all I can find are pdf stat releases with a cutoff of about November 1990. I gather the International Peace Institute (IPI), which runs Peacekeeping.org and built the Peacekeeping Database, gleaned their dataset from these documents. With a little luck the DPKO will one day issue data on older missions. In the meantime, I've yet to see a better collection of data on the topic.
My knowledge of the UN's peacekeeping operations--or Canada's, for that matter--is anything but exhaustive, so I don't have too much to say on the matter. But the story seems pretty self-explanatory.
First off, the early '90s and the supposed last big hurrah of Canadian peacekeeping missions--the Balkans, Somalia, Haiti, Rwanda--were operations where the legwork was done pretty much by others. I find this dispensibility a bit surprising because growing up all the shelling and sniping in Sarajevo was really big stuff. It seemed like Canadian blue helmets and white M113 APCs were on the CBC news every night. But this media coverage was probably an overweighting of Canada's contribution, as the big players in Europe ramped up their peacekeeping efforts to deal with the smouldering tinderbox on their doorstep.
Second, as the UNSC really got behind the peacekeeping idea (or, more accurately, as the end of the Cold War made peripheral regions less important to the UNSC's veto players) and dramatically expanded the number of UN operations it was inevitable that Canada's relative contribution would fall. This is a mathematical certainty for a country with a fixed (if not dwindling) military capacity.
Third, the Harper government takes a lot of heat for getting Canada out of the peacekeeping game, but the contribution trend had in fact stabilized two prime ministers previous. While neither Chrétien nor Martin would take the comparison kindly, the similarity between all three is striking.