IIRC both Stasi and KGB did aim for an almost full coverage of surveillance and informants, not just limiting to a small fraction of the population. Stasi had 500000+ informants (3% or more of population) which had done monitoring, and obviously they wrote reports on much more people than that.
Similarly for KGB; I believe that standard practice was to recruit secret informants e.g. from every course group in universities, so any student activities would be fully covered and you could get a personal report about every student; for 100% of any trips abroad the group had an agent/informant or multiple within the group. So you'd have a small fraction (multiple percent?) of population actively involved in the monitoring, and a majority of people being at least occasionally monitored - as the archives later revealed, an average person should expect that your colleagues, friends and relatives will [have to] write reports on you (corroborated by the fact that any group might include two or more informants, so any omissions would be obvious and cause consequences for the false reporter) and note any expressions of anti-government sentiment.
The aim was to effectively keep a gun aimed at everyone, and they were somewhat successful in achieving that (or at least maintaining that belief) even without modern technologies.
> The aim was to effectively keep a gun aimed at everyone
The aim was to make everyone believe there may be a gun pointed at them even if there wasn't. While that was relatively effective do you know what is even more effective? Actually having a gun pointed at everyone.
Having 500k Stasi informants and spies over its 50 years of existence is a far cry from being able to effectively spy on everyone all the time. And informants are notoriously unreliable due to a whole host of human failings, not least among them being that the people want to gain favor or at least not antagonize the state.
The modern surveillance state would make you inform on yourself via every device or communication channel you use, and at all times, with some human/AI combination making sure very little if anything is missed.
Similarly for KGB; I believe that standard practice was to recruit secret informants e.g. from every course group in universities, so any student activities would be fully covered and you could get a personal report about every student; for 100% of any trips abroad the group had an agent/informant or multiple within the group. So you'd have a small fraction (multiple percent?) of population actively involved in the monitoring, and a majority of people being at least occasionally monitored - as the archives later revealed, an average person should expect that your colleagues, friends and relatives will [have to] write reports on you (corroborated by the fact that any group might include two or more informants, so any omissions would be obvious and cause consequences for the false reporter) and note any expressions of anti-government sentiment.
The aim was to effectively keep a gun aimed at everyone, and they were somewhat successful in achieving that (or at least maintaining that belief) even without modern technologies.