I'm guessing that's because they measured the return rate of institutions:
"Wallets were returned to one of five societal institu-
tions: (i) banks, (ii) theaters, museums, or other cultural establishments, (iii) post offices, (iv) hotels, and (v) police stations, courts of law, or other public offices."
"Wallets were returned to one of five societal institu- tions: (i) banks, (ii) theaters, museums, or other cultural establishments, (iii) post offices, (iv) hotels, and (v) police stations, courts of law, or other public offices."