The Wall Street Journal's Justin Scheck reports:
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.
Books of stamps were one easy alternative. "It was like half a book for a piece of fruit," says Tony Serra, a well-known San Francisco criminal-defense attorney who last year finished nine months in Lompoc on tax charges. Elsewhere in the West, prisoners use PowerBars or cans of tuna, says Ed Bales, a consultant who advises people who are headed to prison. But in much of the federal prison system, he says, mackerel has become the currency of choice.
One reason the mackeral standard has taken off: Hardly anyone actually wants to eat the stuff. Another reason: "each can (or pouch) costs about $1." (So it's pegged to the dollar, then?)
The authorities' response: a steep tax on excess savings, a crackdown on unregulated trading, and, um, limits on credit:
The Bureau of Prisons views any bartering among prisoners as fishy. "We are aware that inmates attempt to trade amongst themselves items that are purchased from the commissary," says bureau spokeswoman Felicia Ponce in an email. She says guards respond by limiting the amount of goods prisoners can stockpile. Those who are caught bartering can end up in the "Special Housing Unit"—an isolation area also known as the "hole"—and could lose credit they get for good behavior.
Bonus link: Every time I blog a story like this, I feel obliged to throw in a link to R.A. Radford's classic article "The Economic Organization of a P.O.W. Camp." If you've never read it before, you should.