Literature review

There are few studies on the issue of participation in water markets. As there are not many water markets documented, gathering information about market transactions and the characteristics of participants is difficult in the context of the developing countries.

There are few research studies similar to water market participation studies, but they do not follow the same goal as this study here. For instance Ranjan et al. (2004) analysed the participation in a water market by mathematical programming, or Hadjigeorgalis (2008) analysed farmer preferences for selecting among different water market choices.

The author could not find many other studies analysing the factors that affect the farmer decisions to participate in a water market. However, some existing studies are reviewed below.

Sharma and Sharma (2006) studied the factors influencing farmers´ decisions to buy groundwater resources for irrigation in Rajestan, India. 280 farmers were selected from eight villages within four districts. The study sample consisted only of farmers who bought

1Office website: http://rcewm.moe.org.ir/HomePage.aspx?TabID=5803&Site=rcewm.moe.org&Lang=fa-IR (accessed 4th Octobor 2011, in persian)

and sold water, whilst those not involved in water trading and those who both bought and sold water were eliminated from analysis, in order to obtain a mutually exclusive sample. The logit model was used for analysis. Significant factors were: size of land holding, negatively; land fragmentation, positively; higher capacity of water lifting device, negatively; and education, positively. Non-significant factors which affected the model positively were: family workers per ha, proportion of high-valued crops and proportion of joint-installed wells. They concluded that this water market, which was based on an undefined property right system, failed to bring social equity as water sellers were charging exorbitant prices to poor, small-scale and marginal farmers. They advised state intervention to regulate the water markets.

Pritchett et al.(2008) studied the factors affecting the willingness to lease, rather than permanently transfer, irrigation water to municipal areas of the South Platte basin in Colorado, USA. Questionnaires were mailed to farmers and 329 (19%) were returned.

Leasing attitudes were measured in this survey using Likert scale ordinal responses. The results were analysed with an ordered logit model. Statistically significant variables which had a negative impact on willingness to lease were: debt ratio, which may indicate a more urgent need to sell water rights; percentage of water supply from groundwater, high levels of which preclude one from leasing water; and proximity to urban centres, which implies increased pressure for urban development and thus increased likelihood of selling of water rights. Statistically significant variables which had a positive effect on willingness to lease were: quantity of acres under irrigation, which may indicate a large quantity of water available for lease; concern for rural communities; and willingness to work with municipalities and other organisations, which is necessary to establish a lease agreement.

Wheeler et al.(2009) investigated whether the adoption of water trading was associated with the same factors that influenced the adoption of agricultural innovations in general.

The data came from water trading during 1998-1999. The sample consisted of 100 buyers, 100 sellers and 100 non-traders. The data were obtained by telephone interview. These three different groups in the sample were compared with each other. Two different analy-ses were done; (1) The logit model was used to study the factors influencing the decision to trade generally, (2) A Multinominal logit was used to compare the factors affecting

decisions to buy, sell, or not trade. Results showed that irrigators were more likely to par-ticipate in allocation trading if they: were older; lived in the region; had a farm plan; had a higher total water entitlement; irrigated more hectares of land; were newer to farming;

had a higher percentage of total irrigated crop land; were female; were education beyond the level of Year 10; had a higher farm operational surplus; believed their farm had low productivity; had a lower percentage of irrigated areas for cattle than for cropland; and did not agree that irrigators should provide water for the environment. They concluded that water trading did conform to many expectations held about the adoption of agri-cultural innovations. Results suggested that water trading can be better categorised as a

“normal” agricultural innovation with benefits mostly for private agents, rather than as a “sustainable” innovation with benefits mostly for the public. They suggested that the adoption of water trading is similar to the adoption of general agricultural innovations.

They found only limited evidence to support the market efficiency hypothesis that water moved from lower value uses to higher value uses.

3.3. Methodology

As the dependent variable in this study, participation in the water market, is a binary variable (0 or 1), a binary response model is required. The linear probability model (LPM) which uses the ordinary least square (OLS) approach has some shortcomings for the analysis of binary variables. Generalised linear models (GLM), with an appropriate link function, can be used to overcome the shortcomings of the LPM. The functional form for a model from the GLM family has to be choosen for the further analysis.

In the binary response model, interest lies primarily in modeling the response proba-bility conditional on a set of covariates:

P r(Y = 1|X) =P r(Y = 1|x₁, x₂, ..., x_m) (3.1)

whereY is the dependent binary variable which has two possibilities: Farmers who bought water from spot water market (Y = 1) and farmers who did not buy water (Y = 0). The vector of explanatory variable X denotes the full set of independent variables. These

variables cover both technical aspects of farm and pump, and household characteristics.

The GLM family are appropriate models for analysing the impact of changes in X on the probability of participation in water market. It can be presented as follows:

P r(Y = 1|X) =F(X, β) =F(β₀+β₁x₁+β₂x₂+...,+β_mx_m) =F(βX) (3.2)

P r(Y = 0|X) = 1−F(X, β) = 1−F(β₀+β₁x₁+β₂x₂+...,+β_mx_m) = 1−F(βX) (3.3)

whereβis the set of parameters that reflects the impacts of changes inXon the probability of participation. The function F(.) takes on values strictly between zero and one (0<

F(.)<1), and could be any cumulative distributions function.

Equation 3.2 shows the probability of the farmer participating in a spot water market and equation 3.3 shows the probability that the farmer does not try to buy water from a spot water market. An appropriate functional form for F ensures that the probabilities are between zero and one. The logit model is used in this analysis, rather than the probit model which is often used in applied economics studies. It must be added that the logit and probit models tend to produce similar results. Different results between two models can be observed with the availability of large data or by using multivariate GLM models,.

In the logit model, F(.) is the logistic function and can be written as follows:

F(βX) = exp(βX)

1 + exp(βX) (3.4)

which is between zero and one for all real numbers. Because of the nonlinear nature of the logit model, maximum likelihood estimation (MLE) is the suitable tool for the estimation of this model (Wooldridge, 2004, ch.17.1).

The goodness fit of the model In GLM models, the deviance is used to assess the adequacy of a model by comparing it to a more general model which can estimate the maximum number of parameters. This general model is called saturated model. Let

L(β;Y) denote the maximum value of the likelihood function for the model of inter-est and let L(β_max;Y) denote the maximum value of the likelihood function for the saturated model. The deviance, also called the log likelihood (ratio) statistic, is D= 2[L(β_max;Y)−L(β;Y)].

In addition, the difference of the deviances between two models (indicated below with subscripts 0 and 1, where model 0 is supposed to be nested in model 1) can be used to test hypotheses (Dobson, 2001, p.86) using the difference of the deviance statistics:

∆D=D₀−D₁= 2[L(β_max;Y)−L(β₀;Y)]−2[L(β_max;Y)−L(β₁;Y)] = 2[L(β₁;Y)−L(β₀;Y)]

(3.5) If both models describe the data well then D₀∼χ²(N−q) and D₁∼χ²(N−p) so that 4D∼χ²(p−q) (Dobson, 2001, p.87).