Here is my impression of the Dow participant - "Me have 10 fingers, me fascinated with 10 fingers, Dow reach major power of 10, me fascinated!!" What if like Fred Flintstone we had 8 fingers? We would be obsessing over octal numbers!
so if we were on a base of 8 instead of 10, 20k in base 8 would be the same actual amount of units as 16,000 units in a base 10 system; i.e., counting in base 8 would be "1, 2, 3, 4, 5, 6, 7, 10" etc. so we would have faced 20,000 and moved on quite a few months ago when 16,000 was first crossed. so you make a very good point: it is merely psychological. but then, markets are strongly influenced by psychology, hence the problem in getting past that number. 19999.67, however, is truly remarkable. then there was the movie, "20,000 leagues under the sea," so maybe there is something to that number, regardless of the base.