ORIGINAL: DocYates
I think another thing to take into effect is the general state f the economy during those years. We had a tremendous boon in the economy during that period. That dollar was good against foreign currency, the stock markets were doing well, and people were more at ease in their jobs and futures.
It's pretty fair to say that economics played a pretty powerful role in the AMA membership. And why shouldn't it, the economy has an effect on everything, including the weather. Of course there are those that could argue Model Aviation magazine drives them away.
Here is membership against the Dow in the same time period. Something look familiar?