What percentage of infants who die as crib deaths remain as earthbound spirits?

This is approximately 50% and therefore it is higher than is the case for adult beings who transition. The reason for the higher frequency becoming earthbound is their low level of experience and the disorientation in awareness, being so new to the earth plane and having not acclimated fully to their new environment. And often it is the match being a poor one with the awakening of great inner discord coming from the akashic records of prior lifetimes being triggered that causes much emotional havoc, and this increases the likelihood they will remain earthbound and be unable to cooperate with the light callers, who do always come for them.