I became a JW via a friend who worked with one and introduced me to him. That was back in 1971 I was 19.
In the congregation I was in it was usually the older generation who had been contacted by door to door work. Most of them between 1950's to 1960's . But from the time I became a JW it was very rare that someone from a doorstep call, through study etc, became a JW. Most were either family or friends of JW's. In fact when I think of it the congregation was really made up in majority by 4 different familes, who over time had intermarried. Then there was the few "outsiders" like myself. Of course if you weren't friendly with one of the families you didn't have much chance of becoming a Min Serv or Elder, or you married into one of them. The Body of Elders was more like a family affair, fathers , sons, brothers, uncles.
As to contacting people on the doors. This became harder through the years. As it became more difficult to find anyone in. Lifestyles had changed, wives no longer stayed at home. People had more leisure time. Sundays were no longer a "day of rest" people were out somewhere.
IN the 5 years before I left only one person who got baptised was actually someone called on and gone through the process. The rest were all the children of JW in the congregation. In fact one year we had no one baptised at all.
Yet we always seem to be reporting about 10 -15 "bible studies" a month.
The number of publishers always seemed to hover around 80 - 85. Even when where hitting 130 - 140 for a Sunday meeting. Today there are 82 publishers , but attendance on Sundays is now 90-100.