Among sixteen major world cities each had twelve wallets dropped as a test of honesty.
The city with the lowest rate of wallet return was Lisbon, Portugal. Only one of the 12 wallets dropped there were returned. And that was by a couple visiting from the Netherlands. In Helsinki eleven of twelve wallets were returned.
It is important to understand that in some cultures it is considered acceptable to keep found money or property. Sort of "it was meant to be" as a transfer of ownership. Whether Portugal is among such cultures is unknown to this blogger.
I like to think that I would attempt to find the owner of money or property that I found regardless the value.