I agree. The numbers should be scaled to # of customers and/or population. To some extent, this is addressed in the text. ATMs reduced the cost of operating a b

I agree. The numbers should be scaled to # of customers and/or population. To some extent, this is addressed in the text. ATMs reduced the cost of operating a branch, so banks opened more branches. It's easy to see that number of tellers has kept up with population growth. US population was ~200e6 in 1970 and is now ~300e6. From that AEI chart, tellers have grown almost as fast. (Made some edits to this comment after I realized I mistook the tellers graph for the ATMs.)