=+d. For practical purposes, we typically only have to worry about modeling tastes accurately at the margin; that is, around the current bundles that consumers/workers are consuming. This is because low-wage workers, for instance, may experience some increases in wages but not so much that they are suddenly high-wage workers, and vice versa. If you were modeling worker behavior for a group of workers and you modeled each worker’s tastes as CES over leisure and consumption, how would you assume r differs for low-wage and high-wage workers (assuming you are persuaded of the empirical validity of the backward-bending labor supply curve)?