Swedish Studies of Reasons and Scale of the Package Effects in Stated Preference Studies
KOTTENHOFF K and SCHMIDT L, Royal Institute of Technology, Sweden
Package effects have been noticed and some possible reasons have been discussed earlier. We have designed two studies especially to address these phenomena. Both studies have included so called secondary attributes, for example comfort and on-board servic
Package effects have been noticed and some possible reasons have been discussed earlier. We have designed two studies especially to address these phenomena. Both studies have included so called secondary attributes, for example comfort and on-board service attributes in trains.
The first study was designed to provoke various reasons for the effects and then measure the magnitude of the effects. It centres on the "valuation reduction". Some of the assumptions taken were decreasing marginal benefits, focusing effects and associations.
Several SP experiments were conducted to test its hypothesis. For example a number of experiments were used to test attribute valuations in three levels. In the middle level packages of attributes were composed and in the upper most level such packages were added to a package of packages. As hypothised the valuations were gradually diminishing.
The second study was designed as a practical solution to surmount most of the package effects without making too long interviews. It uses a two level method composed of an upper level with e well established alternative based pairwise choice method and a lower level with a simplified and quick attribute based "listings method". The upper level is used to estimate the values of attribute packages and the lower level is used two divide the package values into separate and detailed attributes. The result of this study showed smaller valuation reductions than anticipated.
Reasons for the package effects from our own experience and from judgement and choice research findings will be discussed right after the introduction.
Association for European Transport