I'm sure it's not 100%, but I'd bet it's close. Certainly by young adulthood the identical twins I've been around have been relatively easy to distinguish.
That's sort of my theory. But I wonder how much of people's ability to distinguish identical twins is based on physical differences vs more subtle things like how they carry themselves/interact with the world.
Some twins I've known deliberately create physical differences like different hairstyle so other people can recognize them easily without interactions.
