As the article states, the 85th percentile rule is as old as the hills, and the principle about speed differential is as well. All the data I've ever seen would

As the article states, the 85th percentile rule is as old as the hills, and the principle about speed differential is as well. All the data I've ever seen would appear to support it. Do you have any theories as to why states with higher speed limits (or in Montana's case, no speed limits) don't have terribly different worse outcomes from those that have lower ones?