[sethammons]

I found a novel solution by accident to this. I moved to a new area but kept my old number. 99% of my spam calls are from my phone’s area code. If you are not a contact and a number comes up from that area code, it is spam. If it is my new area code, it is a person or business trying to reach me.

You could likely get a far off area coded number.

[acheron]

Same (though "I moved to a new area" happened in 2004). At this point I've just blocked the entire old area code and neighboring ones, aside from existing contacts.

[derwiki]

Yea ignoring unknown numbers from my home state is fairly effective at blocking spam calls.