 There was a decline in the usage and circulation of minted coins by the 10th century as Japanese society began to lose faith in the value of the copper coins as the coins began more diminutive in size and the quality was diluted with an increase in lead due to a shortage of copper.By the mid 10th century, the mintage of copper coins began to phase out and the use of commodity money such as rice, silk, and clothes which all maintained stable value were used in place of the coins.Commodity money began to gain economic value and status and became the stable criteria for evaluating monetary value of various goods and services.