Well, in 1970 you could only do about 10 a day, because you needed to type a cover letter with the hiring manager's name in it. Job search (newspaper "help wanted" ads), envelope stuffing, trips to the post office and so on took time too.

Photocopies were low quality and looked obvious and got you into the trash straight away.

So mass, but compared to population not very mass.

The real start date was Eternal September.