A quick show of hands–who thinks it’s easier to buckle a kid into a booster than it is to buckle a kid into a harnessed car seat?  I think many parents think it’s easier to buckle a child into a booster and that’s why we see the early transition into boosters from harnessed seats.  There are other factors as well for moving a child into a booster seat: it’s less a “baby” seat, the child has outgrown a small/short harnessed seat, the parent is only willing to follow minimum legal safety requirements, it’s easier to move from vehicle to vehicle, the child is more likely able to buckle himself into the seat, there’s less chance for user error.  Or is there?