Ultra-Rare more common than Rare?

[BetsyK]

I consistently use two or three times as many ultra-rare words as rare. Rare is always by far the tiniest portion of my usage. Are there actually more words in a typical board that would be scored Ultra-rare than rare?

[Chelonia]

Yes. I think it's because there are a ton of archaic words that are no longer in use except in word games.