Issued a little less than a year ago, Zimbabwe's bond coin is one of the world's newest monetary units. The bond coin is designed to solve one of the most venerable problems in the pantheon of monetary conundrums; the big problem of small change —a nice turn of phrase coined by economists Tom Sargent and François Velde (excuse the pun). Some background first. When Zimbabweans spontaneously ceased to use worthless Zimbabwe dollars in 2009 they simultaneously adopted a ragtag collection of currencies including the South African rand and U.S. dollar. Unlike cash, coins are heavy—shipping them over to Zimbabwe from the U.S. is prohibitively expensive. So while Federal Reserve banknotes have tended to be used in large value transactions, rand coinage from neighbouring South Africa has been recruited for use in smaller transactions. Unfortunately, there has never been enough coins to conduct trade. The demand for small change is so large that items like gum or candies or IOUs have o...