In reply to design crisis: One way to estimate it might as follows. Estimate the total number of climbers in 1980, 1990, 2000 and 2010 (assume people replace their cams roughly every 10 years). Add all those up and multiply by the fraction of climbers who have a trad rack. Times by 10 (assume 10 cams per rack).
I have the participation numbers for the UK and USA, struggling to find any for Mainland Europe, estimate a quarter have a rack, and the average number owned if 4, guess it should give a rough estimate.
In reply to design crisis: At first I wasn't sure but then I thought about the League of Gentlemen and have settled on a very solid and definite twelve-tee cams sold.