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Pricing Policy Effectiveness is Domestic Water Demand Management

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When m<strong>is</strong>sing variables differ significantly across areas or communities, th<strong>is</strong> may give r<strong>is</strong>e to<br />

a ‘differential intercept model’ – a model in which the regression line has varying intercepts for<br />

different population groups. To estimate these differences across groups, a ‘fixed effects model’ <strong>is</strong><br />

used, based upon dummy variables assigned on the bas<strong>is</strong> of geographical location. 13 Five intercept<br />

dummies have been introduced for Aziz Bhatti, Allama Iqbal, Ganj Baksh, Ravi, and Shalimar towns.<br />

N<strong>is</strong>htar town <strong>is</strong> the benchmark category.<br />

Table 4.1: Notation and Variable Description<br />

Variable Indicator<br />

Qt<br />

AP<br />

MP<br />

DV<br />

W<br />

NR<br />

L<br />

T<br />

Dmo<br />

Dait<br />

Dabt<br />

Dgbt<br />

Drt<br />

Dst<br />

Description<br />

Quantity of water consumed in billing period t<br />

Average price<br />

Marginal price<br />

Difference variable<br />

Wealth<br />

Number of residents<br />

Plot size<br />

Average temperature in period t<br />

Meter ownership dummy<br />

Dummy for residence in Allama Iqbal Town<br />

Dummy for residence in Aziz Bhatti Town<br />

Dummy for residence in Ganj Baksh Town<br />

Dummy for residence in Ravi Town<br />

Dummy for residence in Shalimar Town<br />

Functional Form<br />

As d<strong>is</strong>cussed in chapter two, there <strong>is</strong> no theoretical bas<strong>is</strong> for adopting any specific functional<br />

form. Past studies have typically used linear, semi-log, and double-log forms.<br />

The MacKinnon, White, and Davidson test (MWD test) was used to choose between linear<br />

and double-log forms. The results recommend a double-log functional form. However, there were no<br />

a priori grounds for choosing between semi-log and double-log functions, and therefore, both<br />

functions were estimated. Double-log models have the advantage that their estimators give the<br />

13 Fixed Effect Model (FEM): A model in which the intercept term varies over sampling units but <strong>is</strong> constant<br />

over time.<br />

12

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