We then proceeded to encounter a grand total of one roundabout between there and the southern outskirts of Bradford, and that one was being swarmed by traffic cones. In two places, our SmartNav asked us to negotiate now-non-existent roundabouts, and there were two other places that roundabouts had disappeared since I last drove that way about two years ago. That's an 80% reduction in the 110 miles that we covered.
However, you should not take that as indicating an imminent death of the species. Oh no, far from it, for as roundabouts have been disappearing from some places, they've been appearing in others. On the A1198, we crossed 15 roundabouts on our way home, 75% of the count for the entire journey in a mere 20 or so miles. The bypasses for Papworth and Caxton each add three previously non-existent rotary interchanges.
I suspect that although roundabouts are being taken off the longer, faster routes, they're being added in large numbers elsewhere with the creation of village bypasses. Since such a bypass usually has a roundabout at each end, and with many villages being effectively based on crossroads, I would guess that the modal number of roundabouts per such bypass is three. (Towns tend to have more roads meeting, so for a town bypass, I'd guess four.)