Good question from "new booster law". Most 8 year olds are nowhere near 4'9" tall so if they turn 8 and get moved out of the booster seat, they are still not tall enough to properly sit in the car's seat with their feet resting on the floor. I have an almost 8 year daughter and she is only about 50 inches tall. She most certainly doesn't fit in the seat without a booster. While I totally agree with the new law, there will be a large number of children that turn 8, move out of their booster and will not be properly restrained because they are still not tall enough. It really should be based on age AND height.