What might cause a change in the value of fiat money?

A change in government regulations

Explanation:

Fiat money is a non-convertible and non-backed bond to any physical asset (such as precious metals, gold and silver), but has monetary value commonly accepted in an economy. That is, unlike commodity currencies and currencies, it is a good without intrinsic value, but that has intangible value, coming mainly from its issuer. This type of currency may fluctuate in value with a change in government regulations.

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