I'll go ahead and state my underlying question here: In the Kenpo thread, I questioned a how a particular martial art, as opposed to others, can be specifically designed for "modern day street fighting," when cutting and stabbing weapons, melee weapons, and guns existed in the days Gichin Funakoshi and Kano Jigoro just as they do now; and that if you remove the guns, every possible armed and unarmed scenario you can think of was experienced by homo erectus. One particular argument that @isshinryuronin mentioned, among others, is that your common street thug is more likely have a martial arts background today than he was back then. Now, I'm not going to get into whether or not it's true, or if it even matters - as that's being discussed on that thread. What I'm trying to get to is the likelihood that you'll even run into someone on the streets with a "meaningful amount" of martial arts training. For example, someone who did a 30-day trial when they were 12 years old obviously isn't going to count; so I'm setting it at shodan. And I'll include, like @skribs mentioned, BJJ purple belts and ranks in other martial arts that denote a similar level of mastery.