BMI “works” for populations. It was originally designed and characterized to measure populations, and so it’s the perfect thing to compare massive populations, like states. The majority of people are adequately characterized by BMI, just as they are by waist circumference measures. The “outliers” are vastly more likely to pipe up online.

I believe that in order to edit, you’d submit a pull request to https://github.com/BitEU/Buy. Someone else has recently done just that.