Money don’t last forever

I've heard before that the world's poor has trouble saving. Well, there're lots of reasons for that. But sometimes money just doesn't last. Sometimes moth and rust destroy, thieves break in and steal. Sometimes money withers away.

Here, below, is cent francs. 100 RWF. It's worth about 18 cents USD. They also have 100 RWF in coin version, and this we prefer. We spend these bills as fast as we get them because they feel like they are about to disintegrate in our pockets. Danielle wants me to say something about the velocity of money, MV = PQ, quantity theory of money, but basically small bills get worn out.