This group dropped 100 wallets in a public place (each containing a small amount of cash, a fake $50 gift certificate, and an ID) in front of a hidden camera in order to see who would keep the wallet and who would return it. They then tabulated their results, including a breakdown by age, race, and gender. There’s also a FAQ and a short 8-minute video about the project.
They are careful to make the following disclaimer:
Note: It was not the intention of this experiment to make any particular group look bad, reinforce stereotypes nor to further a hidden agenda of any kind. The actions of a few members in a group should not, of course, be used to judge the whole group.
For those who care, it is technically a crime to take a lost wallet in Illinois, where the test was performed (720 ILCS 5/16-2 “Theft of Lost or Mislaid Property”.) This may or may not be widely known amongst the general population however.