Question: We have information on the consumption choices between X and Y of an individual in two successive time periods. In each she spends all of her income. In the first time period, the price of X is £100, the price of Y is £100 and she consumes 10 units of X and Y respectively. In the second time period, the price of X is £150 and of Y is £150. She consumes 7 units of X and 11 units of Y respectively. Do we have enough information to conclude that her tastes have changed between the two periods?