Research On The Improvement Of The Validity And Reliability Of Non Market Valuation

Non-market evaluation method is an important technology for quantitative assessment of environmental externalities of resource consumption.Among which the stated preference method can better evaluate the non-market value of environmental resources.While this method is accomplished by asking the public’s willingness to pay(WTP)or willingness to accept(WTA)using the questionnaire.Since the design of questionnaire is based on hypothetical scenarios,the question how to improve the validity and reliability of evaluation results has been a concern.Since 1980 s,there has been a large number of research results emerging in the field,various hypotheses has been made and validated to improve the reliability and validity of nonmarket assessments.But a systematic summary is still lacking,some of the hypotheses have not been uniformly validated.In this paper,seven research hypotheses are put forward based on the analysis of factors influencing the validity and reliability of nonmarket evaluation,the methods of improving and testing validity and reliability.Four of the hypotheses are put forword for the first time:(1)the more the number of alternatives in each choice set,the worse the stability of the results;(2)different alternative numbers will result different WTP;(3)when the number of choice sets is within a certain number,the learning effect is greater than the fatigue effect,beyond the number,the fatigue effect is greater than the learning effect;(4)in a certain range,the more reasonable the design,the lower the TWTP(Total Willingness to Pay),the more unreasonable the design,the higher the TWTP.There are conflicting assumptions on the next two existing hypotheses,this paper reaffirms them,namely:(1)although preferences change with the selection experience,but build preference is tend to be stable;(2)WTP obtained from the construction preference is stable and reliable in the short term(during one year or less).One hypothesis has been suggested but not verified: the use of illustrations is better than the use of plain text。In this paper,the environmental externality evaluation of biomass power generation is taken as an example,and the hypotheses are validated by repeated choice experimente and the comparative analysis.The results show that the reasonable combination of the numbers of alternatives and alternatives can effectively improve the validity and reliability of non-market assessment.Preferably,the number of alternatives is 3 or less,under the premise of the three options,to ensure the amount of information obtained is large enough,the number of choice sets is best controlled in about 14.The illustrations should not be applied to all non-market assessments.Before using illustrations,it is important to assess whether the attributes of the evaluation object can be accurately described by pictures.It is advisable to do a pre-survey comparison test to determine the final selection program.