Demand and Stock

Trading

Stock	A villager trade can be used 3, 12 or 16 times, depending on the trade. When the stock is used up, the trade is unavailable until the villager restocks.
Demand change	At each restock, a trade's demand changes by the uses sold minus the uses left unsold. Demand starts at 0.
Demand examples	For a trade with 16 uses: selling all 16 adds 16 demand, selling 12 adds 8, selling 8 changes nothing, selling 4 takes away 8 and selling none takes away 16.
Price increase	Demand above 0 raises the price by base price x demand x multiplier, rounded down. Demand of 0 or less adds nothing.
Worked example	20 Wheat for 1 Emerald has 16 uses and multiplier 0.05. Sold out before one restock, demand is 16 and the price 36 Wheat. Sold out again, demand is 32 and the price 52 Wheat.
Falling demand	A trade that is not used loses demand equal to its full stock at each restock. From demand 32, the 16-use Wheat trade is back at 20 Wheat after 2 restocks without a sale.
Negative demand	Demand can fall below 0. That does not lower the price, but demand has to climb back above 0 before the price rises again.
Missed restocks	When a new day begins and the villager restocked fewer than 2 times the day before, every trade is refilled and loses demand equal to its full stock for each restock missed.
Sales before a refill	Uses sold since the last restock are not counted toward demand when a new day refills the trades this way.