Currency neutrality means that the increase of money supply will lead to the same proportion increase of price level, and has no effect on the actual output level. The traditional theory of money quantity holds that the increase or decrease of money quantity will only lead to the change of general price level in the same direction and proportion, but will not lead to the change of actual income level, and money is neutral.

The neutral reason is that the increase or decrease in the amount of money will only lead to changes in the general price level in the same direction and proportion.