A famous paper in economics showed how cigarettes became a medium of exchange in a POW camp (even leading to booms and slumps depending on Red Cross deliveries). For a long time cigarettes were the money of choice in American prisons as well but today, according to a great piece in the WSJ, the preferred medium of exchange is mackerel.
There’s been a mackerel economy in federal prisons since about 2004,
former inmates and some prison consultants say. That’s when federal
prisons prohibited smoking and, by default, the cigarette pack, which
was the earlier gold standard.
Prisoners need a proxy for the dollar because they’re not allowed to
possess cash. Money they get from prison jobs (which pay a maximum of
40 cents an hour, according to the Federal Bureau of Prisons) or family
members goes into commissary accounts that let them buy things such as
food and toiletries. After the smokes disappeared, inmates turned to
other items on the commissary menu to use as currency…in much of the federal prison system mackerel has become the currency of choice.
I loved this point which raised the possibility of significant mack seignorage.
…Mr. Muntz says he sold more than $1 million of mackerel for federal
prison commissaries last year. It accounted for about half his
commissary sales, he says, outstripping the canned tuna, crab, chicken
and oysters he offers.
Unlike those more expensive delicacies, former prisoners say, the
mack is a good stand-in for the greenback because each can (or pouch)
costs about $1 and few — other than weight-lifters craving protein —
want to eat it.
Thanks to Brandon Fuller for the link.