As we have mentioned, many researches that measuring or estimating attitudes towards taxation are based on the intrinsic motivation for individuals to pay taxes which is sometimes termed their "tax morale ". The tax morale is strongly associated with some psychological factors such as subjective evaluations of tax evasion, evaluations of crime in general, judgments of the government and state in general and so on. The difficulty of measuring tax morale is to quantify subjective norms and include fairness perception in study. We will first introduce a methodology to examine the tax morale by correlating four modules " values, co-responsibility and reciprocity, risk, socio-demographic in descending order and provide a nonlinear model. This nonlinear model can be only interpreted by the sign on the coefficients not their magnitude. .
However, these variables can be difficult to measure through questionnaires merely and many different economic techniques have been used to account for certain biases in results around it. To explore this question, Fehr and Schmidt developed a utility model in 1999 assumed that people get utility from income and disutility from being worse off or better off than other people within a progressive tax system. This utility model led to Doerrenberg and Peichl's effort in trying to prove two hypotheses. The first one is that the more progressive the tax schedule is, the higher an individual's tax morale is and the second hypothesis is that the positive impact of progressive taxation on individual tax morale declines with income. They derived tax morale data from the World Values Survey as dependent variable and used the World Tax Indicator as a measure for the overall progressivity of a tax schedule's progreesivity for main explanatory variable. Although D&P's estimation was successful, the strategy has been criticized for ˜unidentifiable' causality across countries.
