This paper presents a model of the optimal timing of tradeup, which considers consumption and investment motives of homeownership. Households determine the optimal timing of trading up so as to maximize their intertemporal utility of both housing and nonhousing consumption. First we consider current homeowners, who already own a house and expect that they trade up to a more valuable house at some point in the future. Housing appreciation tends to induce an earlier optimal timing of trading up. Moreover, housing appreciation makes current homeowners better off in terms of welfare. However, current homeowners suffer from a rise in mortgage interest rates. Second, we consider first-time home buyers, who have decided to buy a house and expect to trade up to a more valuable house in the future. Their initial housing consumption is determined by an initial downpayment constraint. In this case, the effect of housing appreciation on the optimal timing of trading up is ambiguous and, unlike current homeowners, first-time home buyers suffer from housing appreciation. Moreover, as current homeowners, first-time home buyers suffer from a rise in mortgage interest rates. Most of the theoretical analytic results are ambiguous. Accordingly, we perform numerical simulations based on the theoretical model in order to determine the most likely comparative effects for a stylized set of parameters. As is apparent, the model captures the recent observations on homewner mobility and suggests that macroeconomic variables such as housing appreciation and mortgage interest rates effect the optimal timing of trading up and homeowner's welfare. Nevertheless, the model in this paper has several shortcomings, which should be the subject of future research. First, transaction costs are ignored. If transaction costs are incorporated, the lock-in effect from a rise in mortgage interest rates is well explained. However, the general analysis above is not altered in any essential way. Second, multiple moves are not considered in this model. Therefore, we concentrate on the timing of one tradeup as opposed to the timing and frequency of trading up. In a different vein, it would be interesting to test empirically the importance of the effects of macroeconomic variables on trading up by using microdata.

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• Economia e Gestão - Ciências Sociais
• Geografia Económica e Social - Ciências Sociais