These examples again demonstrate Marshall’s observation that demand and supply together determine price and quantity. Recall from Chapter 1 Marshall’s analogy: Just as it is impossible to say which blade of scissors does the cutting, so too it is impossible to attribute price solely to demand or to supply characteristics. Rather, the effect that shifts in either a demand curve or supply curve will have depends on the shapes of both of the curves. In predicting the effect of shifting supply or demand condition on market price and quantity in the real world, this simultaneous relationship must be considered. Application 10.2: Ethanol Subsidies in the United States and Brazil illustrates how this short-run model might be used to examine some of the politics of government price support schemes.