The Random Walk': A Study of Coins Lost and Found in an Urban Environment

A study was made of one thousand coins lost and found while walking in an Australian urban environment over a period of ~ 28 months during 2006-2008. The numbers of each denomination found showed a strong relationship with the numbers in circulation and the product of the denomination with the diameter. Also, the mintage dates of coins recovered were generally representative of those in circulation. The number of coins found per walk showed a distinct departure from a Poisson distribution due partly to the occurrence of coin clusters. Overall, coins were more likely to be found in commercial zones, near food outlets and in fine weather. Surprisingly, there was no apparent correlation with population density. Residence times before recovery were estimated to be a maximum of 2-3 days. Some estimates of permanent coin loss on the road and to landfill were made and compared with attrition rate data.