if you use your card for gas..they know where you are..and can go from there...narrows the field. Using card for groceries they can tell if you have children, pets, health issues etc. by what you buy ..stores list all your items now.
My wife saw an ad for the “National Consumer Panel” and signed up for it thinking it was a way to earn money in her spare time. They (Nielsen and IRi) sent her a scanner with a keyboard. The instructions said that *anyone* in the household who bought *anything*, even for cash, had to scan the items and enter a price and where they bought them, info about who they were shopping with, etc. Unbelievable. And they didn’t really offer money for it either. I sent the thing back and told them where they could shove it.