title: An examination of sources of sensitivity of consumer surplus estimates in travel cost models.
abstract: We examine sensitivity of estimates of recreation demand using the Travel Cost Method (TCM) to four factors. Three of the four have been routinely and widely discussed in the TCM literature: a) Poisson verses negative binomial regression; b) application of Englin correction to account for endogenous stratification; c) truncation of the data set to eliminate outliers. A fourth issue we address has not been widely modeled: the potential effect on recreation demand of the interaction between income and travel cost. We provide a straightforward comparison of all four factors, analyzing the impact of each on regression parameters and consumer surplus estimates. Truncation has a modest effect on estimates obtained from the Poisson models but a radical effect on the estimates obtained by way of the negative binomial. Inclusion of an income-travel cost interaction term generally produces a more conservative but not a statistically significantly different estimate of consumer surplus in both Poisson and negative binomial models. It also generates broader confidence intervals. Application of truncation, the Englin correction and the income-travel cost interaction produced the most conservative estimates of consumer surplus and eliminated the statistical difference between the Poisson and the negative binomial. Use of the income-travel cost interaction term reveals that for visitors who face relatively low travel costs, the relationship between income and travel demand is negative, while it is positive for those who face high travel costs. This provides an explanation of the ambiguities on the findings regarding the role of income widely observed in the TCM literature. Our results suggest that policies that reduce access to publicly owned resources inordinately impact local low income recreationists and are contrary to environmental justice.
authors.affiliation: Ohio State University Extension, Department of Extension, The Ohio State University, 416 Park Drive, Apt B, Wooster, OH 44691, USA. Electronic address: blaine.17@osu.edu.
authors.forename: Thomas W
authors.initials: TW
authors.lastname: Blaine
authors.affiliation: Ohio Sea Grant College Program and Ohio State University Extension, Department of Extension, The Ohio State University, 99 East Erie Street, Painesville, OH 44077, USA.
authors.forename: Frank R
authors.initials: FR
authors.lastname: Lichtkoppler
authors.affiliation: Fairport Harbor Fisheries Research Unit, Ohio Department of Natural Resources, Division of Wildlife, 1190 High Street, Fairport Harbor, OH 44077, USA.
authors.forename: Timothy J
authors.initials: TJ
authors.lastname: Bader
authors.affiliation: Sandusky Fisheries Research Unit, Ohio Department of Natural Resources, Division of Wildlife, 305 E. Shoreline Drive, Sandusky, OH 44870, USA.
authors.forename: Travis J
authors.initials: TJ
authors.lastname: Hartman
authors.affiliation: Ohio Sea Grant College Program and Ohio State University Extension, Department of Extension, The Ohio State University, 1 Government Center, Suite 550, Toledo, OH 43604, USA.
authors.forename: Joseph E
authors.initials: JE
authors.lastname: Lucente
mesh_terms: D004777:Environment; D006801:Humans; D007182:Income; D018803:Models, Economic; D011640:Public Policy; D011998:Recreation / Q000191:economics*; D014195:Travel / Q000191:economics*
keywords: Consumer surplus; Environmental justice; Fishing; Recreational value; Revealed preference modeling; Travel cost