What moral basis does the average atheist have? What is their grounding principle of behaviour and knowledge?

Did you know that there are far fewer Atheists in jail and prison than believers. Less than 2% percent of all Convicted felons in the USA are Atheist, compared to the 5% of the population not in Prison. It would seem that the theists, supposedly more moral than the godless Atheists, commit more crimes than do Atheists. Go figure.