Chapter 18: Transport Welfare Benefits in the Presence of an Income Effect

This paper presents new evidence that the error in estimating the economic welfare of a transport scheme can be very large. This is for two reasons. Firstly when cost changes are large the income effect can be significant. This means the change in consumer surplus is no longer a good estimate of the compensating variation — the true measure of welfare benefit. Secondly, in the presence of large cost changes estimating the change in consumer surplus using the Rule of Half can lead to large errors. The paper uses a novel approach based on stated choice and contingent valuation data to estimate the size of this error for the situation of the provision of fixed links to islands in the Outer Hebrides of Scotland.