A Miron is a unit used in the Wurm's economy logging system. It basically stands for a Million iron. (Iron coins are the smallest currency unit in Wurm). This means that a Miron is equal to a Gold coin. In the beta version of Wurm, the Miron values would stay exactly the same throughout the map, unless the developers or game masters spawned some extra money. Now, because of the Wurm store, you can buy silver coins which can increase the values of Mirons in the economy. By looking at the graphs, the number can decrease, but the graphs do not count the amount of money in player's inventories according to the legend, so players may be taking money out of their banks, village upkeep and shops and putting it back in.
Bank of Wurm - about the currency of Wurm