You would be really really suprised. This is out of the scope of this forum, but lemme discuss it a tiny bit.
Drawing vs a drawn gun is very possible with practice. It takes work and practice, but if one is going to carry a gun every day, then one might as well learn to use it right.
Firstly, most criminals arent that great with guns, this is not saying underestimate your opponent, but it is saying that there is a fighting chance. Many things suggest that defiance alone will make some criminals hesitate.
Second, nothing is keeping you from moving. Depending on the position, this can be a big part of life or death. One must be calm, controlled and swift for it to work.
My dad and I, in adition to some friends, have simmed situations out using airsoft pistols or the real deal (but checked and unloaded of course). The results are very encouraging. I have gotten to the point that in an open carry holster (i dont have a concealed carry holster, namely because i cant carry till im 21) with a full sized 1911, and dad droping a quarter at waist level for timing, I can have the weapon out in a weaver stance and pull the trigger, before the quarter hits the ground. If you dont believe, I can record it and host it on my site.
There is most definately a fighing chance in that situation, believe it or not.