45.3% - The chance your open face will do NOTHING in a crash.
Step 1: Find a trash can.
Step 2: Deposit that open face decoration.
Step 3: Go buy a full face. Find one that is aerodynamic, Sharks, Nexx, and Shoei tend to have the best aerodynamics in my experience.
Step 4: Enjoy no more or vastly reduced buffeting.
Seriously, if you like having a chin use a closed face helmet if tolerable in the weather your ride in. Open face helmets are a joke.
I did ride with an open in Hawaii in the summer months, it's just not reasonable to wear a full face in the middle of the day, in that heat and humidity, sitting in traffic. That said, I just treated it like not wearing a helmet, rode very defensively and didn't really play very much.
I put the image up front because I know people will start reading and skip over it if they're open face fans. Closed faces are vastly more aerodynamic, while being more protective, and they help cut decibel levels (even a stock roadster @ 70mph will cause long term hearing loss).