"I soon realized that there were two kinds of people who were buying newspapers: people who had just moved and people who had just gotten married." I wonder ho

"I soon realized that there were two kinds of people who were buying newspapers: people who had just moved and people who had just gotten married." I wonder how he figured this out as all he initially had to go by was the phone numbers. For example, did he casually chat up his cold calls and make mental notes about what they talked about and who was buying or was he being more methodical in some way?