Answer:
An increase in y which is per capital income will cause demand curve to shift left.
Step-by-step explanation:
In theory of demand, the following are two categories that can happen to the demand curve:
1. Change in quantity demanded: This is a movement along the demand curve which is caused only by the change in the price of the commodity. When the price falls, there will be a movement to the right along the demand curve indicating an increase in quantity demanded. But when the price increases, there will be a movement to the left along the demand curve indicating a decrease in quantity demanded.
2. Change in demand: This is a bodily shift of demand curve caused by others factors affecting the demand of a commodity except price. The demand curve will shift to the right when there is an increase in any of the factors that has positive effect on the demand for the commodity to indicate an increase in demand for the commodity. However, the demand curve will shift to the left when there is an increase in any of the factors that has negative effect on the demand for the commodity to indicate a decrease in demand for the commodity.
From the question, y falls into the second category which is Chang in Demand. Since the sign before 2y in the demand curve for Widgets is negative, that implies that y as a factor affecting the demand for Widgets has a negative effect on the demand for Widgets. Therefore, an increase in y which is per capital income will cause demand curve to shift left.