h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

How could pennies be in short supply? They seem to keep breeding in my pocket. By the end of the day I have more pennies than I started out with and unfortunately they seem to be eating the other coins to feed their sexual activities.

It's simple. Everyone has a large supply of pennies in their pocket. As the amount of pennies stored in pockets accross the nation grows every day there are fewer and fewer pennies to be found in the cash registers of all shopping precincts. Therefore there is a shortage of pennies even though there are still lots of pennies in existence. If everyone were to spend pennies or cash them in at their bank or whatever then the pennies would get back into circulation quicker, so the shortage would disappear. However, the pennies are small and near worthless, so they are of course hard to spend. Who wants to spend five minutes at the checkout counting out pennies, only to give them to the afformentioned checkout girl who has to count them all out again to make sure they are in the correct quantities. This is obviously a design flaw.