Comment by gbacon

A fascinating chapter in The Power of Habit by Charles Duhigg describes market-basket analytics at Target. They wanted to be able to determine whether a shopper is pregnant because that is an event that they believed women to be willing to reconsider their otherwise steadfast shopping brand loyalty. They got too good at their target ad mailers and so had to throw in decoys like motor oil and lawn equipment.

The tipoff for expecting women was purchases of larger quantities of lotion and washrags.