In this equation <strong>the</strong> levels of , and , that occur in <strong>the</strong> numerator refer to <strong>the</strong> situation before <strong>the</strong> extension of <strong>the</strong> metro network. 25 corresponds with <strong>the</strong> change ∆ln ,, in log income can be determined as: The change in income itself that ∆ ,, 1 ∆ ,, (A5) If households would not change <strong>the</strong>ir location, housing type or car ownership position, this would suffice to compute <strong>the</strong> welfare impact of <strong>the</strong> change in <strong>the</strong> metro network. However, <strong>the</strong> changes in <strong>the</strong> utilities of <strong>the</strong> choice alternatives that occur as a consequence of <strong>the</strong> extension of <strong>the</strong> metro network will induce some households to change <strong>the</strong>ir residential location, car ownership position or perhaps even <strong>the</strong>ir housing type. To take this into account as well, we use <strong>the</strong> results of De Palma and Kilani (2003). We start by defining ∆ as <strong>the</strong> largest of <strong>the</strong> conditional compensating variations: ∆ max ,, ∆ ,, (A6) DePalma and Kilani (2003) show that <strong>the</strong> unconditional compensating variation is always between <strong>the</strong> minimum and <strong>the</strong> maximum of <strong>the</strong> conditional compensating variations. To be able to compute it exactly we define functions ,, as follows: ,, ,, , , , , , , ; , (A7) where <strong>the</strong> values of , and , refer to <strong>the</strong> situation with <strong>the</strong> extended metro network. Clearly, if ∆ ,, , ,, is equal to <strong>the</strong> utility household I experienced before <strong>the</strong> ∗ extension of <strong>the</strong> metro network. Now define: ,, max ,, , ,, ∆ ,, and let ∗ denote <strong>the</strong> logit choice probabilities defined on <strong>the</strong> basis of <strong>the</strong>se utilities: 26 25 The income level that occurs in <strong>the</strong> denominator refers (<strong>from</strong> <strong>the</strong> derivation of (A.3)) to <strong>the</strong> situation after <strong>the</strong> extension of <strong>the</strong> metro network, but we assume throughout that household income does not change because of <strong>the</strong> extension of <strong>the</strong> metro network. 26 This equation is analogous to (2) for <strong>the</strong> generator function of <strong>the</strong> multinomial logit model. 50
,, ∗ ∗ ,, ∑ ∑ ∑ ∗ ,, (A8) This brings us – finally – in <strong>the</strong> position to define <strong>the</strong> expected value of <strong>the</strong> unconditional expected value of <strong>the</strong> compensating variation : 27 ∆ ∆ ∑ ∑ ∑ ,, ∗ (A9) ∆ ,, De Palma and Kilani (2003) suggest to evaluate this expression through simulation. Since <strong>the</strong> integral has to be computed is one-dimensional, Gaussian quadrature is also feasible and we used this technique (see Judd, 1999, chapter 7). 27 It can be shown that (A8) reduces to <strong>the</strong> change in <strong>the</strong> logsum when utility is linear in income. 51