Very popular here too. (The Netherlands)
More than a jar per week usage in this household. Often two.
What hardly anyone eats here are peanutbutter jelly sandwiches though. I heard that that was a typical north american thing. Now I'm wondering if that's true.
When you look at breadtopings that don't need a fridge in a supermarket, most space will be for jams. Chocolate topings and peanutbutters come second. Defenitely popular here.
Smallest space is for marmite.