Dirty money: an investigation into the hygiene status of some of the world's currencies as obtained from food outlets

total of 1280 banknotes were obtained from food outlets in 10 different countries (Australia, Burkina Faso, China, Ireland, the Netherlands, New Zealand, Nigeria, Mexico, the United Kingdom, and the United States), and their bacterial content was enumerated. The presence of bacteria on banknotes was found to be influenced by the material of the notes, and there was a strong correlation between the number of bacteria per square centimeter and a series of indicators of economic prosperity of the various countries. The strongest correlation was found with the “index of economic freedom,” indicating that the lower the index value, the higher the typical bacterial content on the banknotes in circulation.