Sometimes nothing, sometimes everything :) From what I've been told, the books are so outdated that what was scarce back when they were made may mean they are still 'Scarce', have become 'rare', or have turned 'common'. I would say it is a pretty good indicator and if you are trying to sell it or keep it, I'd use the word 'scarce' because RIC and books are the current 'renowned' books of our time.