Rear facing is much, much safer than forward facing. There are many articles that discuss the reasons why your children should remain rear facing for the first full year and 20 pounds. Many of these same articles discuss that consequences of injury drop dramatically after the first year of life. However, it does not state that there are no consequences. The consequences may no longer be death from a completely severed spinal cord, but simply life-long injury, including complete paralysis. Research studies suggest that until children are at least four years of age, they are helpless in withstanding crash forces as well as adults; henceforth they should remain rear facing.
In a crash, severe or deadly injuries are generally limited to the head and neck, in the case of a child being in a harnessed seat. When a child is in a forward facing seat, there is an incredible amount of stress put on the childs neck, which must hold the large head back. A small childs neck upholds great amounts of force in a crash. The straps hold the body back while the head is thrown forward, which can break the spinal cord. Also, the childs head is at a greater risk in a forward facing seat as well. In a crash, the head is thrown outside the confines of the seat and can make dangerous contact with other passengers or intruding objects.
Rear facing seats do a extraordinary job of protecting children simply because there is little to no force applied to the head, neck, and spine. When a child is in a rear facing seat, the head, neck and spine are all kept fully aligned and the child is allowed to ride down the crash while the back of the child seat absorbs the bulk of the crash force. The childs head is contained within the seat, and the child is must less likely to come into contact with anything that might cause head injury.