I just had a thought about how we think some royals are work-shy and others work their butts off. But some of these royal families live in small countries, with even smaller populations. So they just plain don't have as many hospitals or social-work foundations or schools or museums to visit, bless, open, close, unveil etc. So what if you divided the population of a country that has a working royal family by the number of working royals. The higher the number, the greater the number of appearances would be expected per royal. And in a low-population country, the working royals could coast a bit more.
For example, just how many hospitals or military units does Luxembourg have? I would suppose you could hit most of them on one streetcar run . . . .
I'm not sure about the relative populations of the royalist countries except that I know The Netherlands is very densely populated, while there are big stretches of Sweden and Norway that aren't much but forest or farmland. The UK has a lot of very densely populated urban areas but still enough open land where there aren't a lot of people.