About as many times, but the key thing is that the horn is only useful if I'm static since otherwise it's faster for me to evade than honk. I estimate ~0.5 s to 1 s net delay to action if I were to honk, with 0.5 s to 1 s delay in action from other person if they're fast. At a 2 s delay, unless I'm not moving, evasion + braking seems superior. And evasion is made harder while honking. I've had many times where people run red lights in front of me (I live in SF) but I've never honked. It's frequently too late to do anything so I just brake.