Top-five countries are not surprising...
#1 USA - 48.94% registrations of .CO domains
#2 UK - 13.05%
#3 Colombia - 7.95%
#4 Canada - 4.05%
#5 Australia - 3.68%
The following five are more surprising...
#6 Germany - (only) 2.06%
#7 India -1.75%
#8 China -1.44%
#9 Poland - 1.35%
#10 France -1.17%
Germany... with only 2.06% of .CO domains (Germany is biggest ccTLD, #1 in .EU registrations and #2 in .COM registrations). Only 2.06% of .COs. Surprising?
Poland... 1.35% of .CO? Surprising, very surprising... Poland is not in the top-10 of .COM registrations, so why the hell, Poles started using .COs? Trademarks protection - definitely not due to the fact that there is not much well known trademarks owned by Polish businesses. Business expansion - rather not - Polish companies expand generally into European Union, not outside EU.
And France... yep, past restrictions in .FR registrations were driving factor for French businesses to register .COMs in the past 10 years. But now? Probably because of trademarks protection.