About 3 years ago the county that our family ranch is in went to a 13" rule (Inside spread) it has improved the age structure as a whole in the county.... This year they added a ton of counties in Texas with the same rule, approx. 60 counties total in the state...
I think all in all it helps with age structure but some of the deer slip through the cracks that really need to be taken... IE: a 5 1/2 yo that is not 13" wide but is really tall and heavy!!!! With that said, I think the good out weighs the bad!!!!