#1 Have you heard of google?
http://lmgtfy.com/?q=aamc statistics
#2 Your GPA is a single component in figuring out your academic prowess. It is completely meaningless without more context. First, your GPA is modulated by the school you go to, your major, the rigor of your curriculum, extenuating circumstances, etc. Second, a student's MCAT will obviously answer a lot of questions regarding your ability to assimilate material.
For example, if you are a Physics/Econ major at U of Chicago taking 20 credits a semester and work 30 hours/week to provide for younger siblings, a 3.4 is going to be very different than you got a 3.4 being a Biology major at *pick most any school in the country* taking the standard 15 credits/semester. Do you get a hard 'GPA bump' because of those factors, no. Will it be seen as 'better' than a 3.7? No. But, coupled with a good MCAT score, people tend to care a lot less about a low GPA.
#3 When you have a lower GPA, you have to consider that there are thousands of applicants with a better GPA than you. Therefore, the rest of your application has to have something else that is better than them to get attention and ultimately get you in.
#4 In summary, there are people with 3.4/31s that get into medical school every single year. They are generally the people who a) applied smart/broad and b) who have strong things outside of their academic metrics that make them appealing to adcoms.