https://www.google.com/amp/s/www.forbes.com/sites/kashmirhill/2012/02/16/how-target-figured-out-a-teen-girl-was-pregnant-before-her-father-did/amp/ https://www.

https://www.google.com/amp/s/www.forbes.com/sites/kashmirhill/2012/02/16/how-target-figured-out-a-teen-girl-was-pregnant-before-her-father-did/amp/ https://www.google.com/amp/s/www.forbes.com/sites/kashmirhil... They were doing this in early 2000s, can't imagine how sophisticated the same type of system is now.