Migration is an investment: it involves fixed, unrecoverable costs and
uncertain future returns. If migration can be postponed, the option v
alue of doing so may have positive value. Migration may not occur for
a range of individuals who would otherwise migrate on a net present va
lue basis. This paper models the migration decision using ideas develo
ped by Pindyck (1991) and Dixit (1992). The option value of waiting is
related to the interest rate, fixed costs, and especially uncertainty
governing the evolution of income at home and abroad. The ''bad news
principle'' predicts that only unfavourable states of the world will a
ffect the value of the migration option. In a rational intertemporal e
quilibrium of two regional labour markets, low migration rates may coe
xist with large or even increasing current wage differentials.