The photos bring back memories of how much of a generation gap there was at assemblies. By that I mean that you would see a lot of high-school age JWs walking around trying to catch the attention of the opposite sex. But you wouldn't see that many young 20 somethings. By that age they were married, disfellowshipped, or just stopped attending altogether.
I went to one day of the district convention last year as a favor to my parents. It was amazing to see the number of teenagers just walking around aimlessly and the gap in the 20-30 crowd. It never made an impression of me when I was a kid because I always kind of viewed myself as an adult, but going back now as a grown man, I could see the age gap clearly.