Ken Vincent examined 1667 published ADC cases and found that 336 or 20.1% could be considered evidential. These cases fall into three commonly researched categories:

(1) Apparitions appearing before the experiencer’s knowledge of the death of their loved one (APD) numbered 180 or 10.8% of the sample.
(2) Apparitions appearing to multiple witnesses (AMW) numbered 57 or 3.4% of the sample.
(3) Apparitions that convey knowledge unknown to the experiencer that is later proven to be true (AKU) numbered 99 or 5.9% of the sample.
Read Ken Vincent's excellent analysis.