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help for spike                                               Joao Pedro Azevedo
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Spike model for Williness to Pay


        spike {s} {t} {bid}

    where

    s is the variable that indicates if the respondent would like to
    contribute at all to the project (S =1 if WTP>0).

    t is the variable that indicates if the repondent would like to
    contribute to the project at the price offered (T =1 if WTP>AMOUNT).

    bid is the variable that reports the bid value offered to the respondent.

Description

    spike command allows for a non-zero probability of zero
    willingness-to-pay in referendum-style contingent valuation experiments
    as suggested by Kristrom (1997). This property is particular usefull in
    experiments in which a large fraction of the population chose not to
    consume good being offered. In such circunstances the use of traditional
    parametric models based on probit and logit models are likelly to predict
    a negative willingness-to-pay.


Examples:

    . use ferry dataset (http://www-sekon.slu.se/~bkr/)
   
    . spike s t bid
   

Reference

    Azevedo, Joao Pedro. What is the Value of Educational Broadcast?
    (February 2009). Available at SSRN: http://ssrn.com/abstract=1332786.

    Kristrom, B. (1997). Spike Models in Contingent Valuation. American
    Journal of Agricultural Economics 79(3), 1013-1023.

Authors

    Joao Pedro Azevedo
    jazevedo@worldbank.org

Also see

    turnbull if installed.