The marginal price elasticities estimated by Martinez-Espineira conforms to expectation. The price specification that accounts for the changing proportion of water users in each block yields a higher elasticity (-0. 47) compared to the spec- ification ignoring this feature of the data. However, this difference is not found to be statistically significant, a result attributed to the low power of the test (small sample size limiting the accuracy of estimates). In conclusion, the paper provides a theoretically correct price specification for demand functions under block pricing and aggregate...