Evaluating Elasticity of Income and Price on Water Demand Using Pollak–Wales Method

Document Type : Research Paper


1 Ph.D Student of Economics, Ferdowsi University, Mashhad

2 Assist. Prof. of Water Engineering, Ferdowsi University, Mashhad

3 Assist. Prof. of Economics, Ferdowsi University, Mashhad


Iran is located in an arid and semi-arid region and will be joining the ‘Thirsty States’ by 2025. However, water use efficiency and water services seem to be low and inadequate, as they do not match the emerging conditions of water scarcity. As part of the research efforts required to address the problems in this area, this paper endeavors to use a simple, efficient, precise, and practical method for determining the income and price elasticity of the domestic drinking water demand. The household income in this method is replaced by a good, measurable substitute index which is the household land and building areas. Log-log functions are presented for different blocks for the statistical period 2001-2004. Correlation coefficients obtained were above 40% in all the functions. The average income elasticity ranged from 0.704 to 0.411 for the first to the fifth blocks, respectively. This shows that water is a necessary and non-substitutable commodity in the household portfolio. The price demand elasticity was estimated using the modified Pollak–Wales method, price variations over two different time periods, and income elasticity over the statistical period. The price elasticity value varied from -0.3 to -0.01 for the second to fourth blocks, respectively. This indicates the inelasticity or low elasticity of water for current prices.


1- Shaoliu, L. (2002). “Water pricing towards sustainability of water resources: A case study in Beijing.” J. of Environmental Sciences, 14(4), 518-523.
2- Strand, J., and Walker, I.(2004). “Water markets and demand in central American cities.” J. of Environment and Development Economics, 10, 313-335.
3- Briscoe, J. (1996). “Water as an economic good: The idea and what it means in practice.” Proc. of the ICID World Congress,Cairo,Egypt.
4- Renwick, M., and Archibald, S. (1998). “Demand side management policies for residential water use: who bears the conservation burden?” Land Econ., 74(3), 343-359.
5- Buch Muller, T.C., and Feldstein, P.J. (1997). “The effect of price on switching among health plans.” J. of Health Economics, 16(2), 231-247.
6- Fernando, A., Ángeles, M., Valiñas, G., and Espiñeira, R.M. (2003). “Estimation of residential water demand: A state of the art review.” J. of Socio-Economics, 32, 81-102.
7- Kostas, B., and Chrysostomos, S. (2006). “Estimating urban residential water demand determinants and forecasting water demand For athensmetropolitan ares, 2000-2010.” J. of Economics, 1, 47-59.
8- Schoengold, K., Sunding, D.L., and Moreno, G. (2006). “Price elasticity reconsidered: Panel estimation of an agricultural water demand function.” Water Resources Res., 42, 1010-1029.
9- Espineiro, R.M. (2002). “Residential water demand in the northwest of Spain.” Environmental and Resource Economics, 21, 161-187.
10- Morgan, W.D., and Smolen, J.C. (1976). “Climatic indications in the estimation of municipal water demand.” Water Resource Bulletin, 12(3), 511-518.
11- Al-Qunaibe, T.M.H., and Hohanston, R.S. (1985). “Municipal demand for water in Kuwait: methodology issues and empirical results.” Water Resources Res., 10(6),433-438.
12- Cocharan, R., and Cotton, A. (1985). “Municipal water demand study, Oklahoma cityand Tulsa, Oklahoma.” Water Resources Res., 15(7), 941-943.
13- Griffin, R. C., and Chang, C. (1990). “Pretest analyses of water demand in thirthy communications.” Water Resources Res., 26(10), 2251-2255.
14- Hoglund, L. (1999). “Household demand for water in Swedenwith implication of a potential tax on water use.” Water Resources Res., 35(12), 3853- 3863.
15- Kracman, D.R. (2000). “Estimating water demands for irrigation oistricts on the Lower ColoradoRiver.” <http:// www.ce.ateaxs.edu/stu/Kracmadr/tern 1.htm>, (Sep. 11, 2007).
16- Onjala, J. (2001). “Industrial water demand in Kenya.” <http:// www.ce.environmental-economics.dk/papers/water kenya.pdf>, (Sep. 11, 2007).
17- محمدی دینانی، م.، و اکبری، ح. (1379). تخمین تابع تقاضای آب شرب در شهر کرمان. فصلنامه پژوهشهای اقتصادی ایران، 7، 67 - 77.
18- Aghthe, D. E., and Billings, R. B. (1980). “Dynamic model for residential water demand.” Water Resources Research, 16 (3), 476-480.
19- Danielson, L. E. (1979). “Analysis of residential demand for water using micro time-series data.” Water Resources Research, 15 (4), 763-767.
20- Williams, M., and Shu, B. (1986). “The demand for urban water by customer class.” J. Applied Economic, 18, 1275-1289.
21- Steven, T. H., Miller, J., and Wills, C. (1976). “Effect of price structure on residential water demand.” Water Resource Building, 28 (4), 681-685.
22- Pollak, R.A., and Wales, T.J. (1978). “Estimation of complete demand system from household budget data.” American Economic Review, 68(3), 348-359.
23- صالح‌نیا، ن. (1385). قیمت‌گذاری آب شرب شهری با استفاده از مدل رمزی، مطالعه موردی شهر نیشابور. پایان‌نامه کارشناسی ارشد، دانشگاه فردوسی، مشهد.
24- Pushpangadan, K., and Murugan, G. (1998). “Pricing with changing welfare criterion: An application of Ramsey-Wilson Model to urban water supply.” Center for Development StudiesThiruvananthapuram,Indiana.
25- شرکت مهندسین مشاور پارس کنسولت. (1383). طرح مطالعات آب به حساب نیامده نیشابور، تهران.