help for spike                                               Joao Pedro Azevedo

Spike model for Williness to Pay

spike {s} {t} {bid}


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.


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.


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


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.


Joao Pedro Azevedo jazevedo@worldbank.org

Also see

turnbull if installed.