While This May Seem Like an Urban Legend, there was a time when the default rate, or unknown keycode capture rate, was 4%.
I recall about 15 years ago having meetings with a catalog call center team when the default climbed to 8%, and we were aggressively tackling the situation. Together we problem-solved and instituted pink- and yellow-tinted boxes to help shoppers find their customer numbers and keycodes. We avoided using certain characters in the keycode such as B, I and O, because customers often visually misinterpreted these as 8, 1 and 0.
Call center representatives knew that key codes equated to lists (segments) that marketing used for mailings. If marketing invested dollars into List A and the results were strong, then marketing would mail significantly more of List A next time.
If the call center didn’t capture the data correctly, the campaign would fail, dollars would be wasted, and everyone would be held accountable.