This is probably a stupid question as I don't know much about economics, please bear with me. My question is; why can't a country insist on the worth of their currency relative to the dollar. For example, why can't a country like Nigeria insist that 1 naira is equal to 1 dollar and that is accepted worldwide for trading. I guess my real question is, why does the value of a country's currency increase or reduce relative to the dollar or other currencies. Thanks.