That's the whole theory behind 20-30% being
effective herd immunity. That some segment of society has effectively removed themselves from the herd for now by isolating a lot more, and being careful when they are out.
Well also there's some buffer. So maybe it's like 60% work from home office drones like me - taking lots of precautions, who are very unlikely to get it unless they get complacent. Also retired/at-risk people who are being careful. Nursing homes have much better protocols now. Etc.
https://www.theatlantic.com/health/a...avirus/614035/
This article makes a lot of the points. This is the first pandemic with massive social distancing. It's a whole new ballgame.