Résumé
This paper solves a second-best problem where a government has in particular to choose whether to tax financial inflows (capital controls) or not, and when. A multi-stage optimal control technique is used to this end. First, it is shown that it is optimal to switch in finite time from capital controls to full financial liberalization (zero tax on capital inflows) whenever a measure of total wealth is above a certain threshold. In particular, a too large initial debt makes financial liberalization sub-optimal. Second, our analysis suggests that capital controls should be used countercyclically: booms should be responded by more financial liberalization while recessions should rather lead to more stringent capital controls. Third, when public expenditure is chosen in order to maximize social welfare, financial liberalization is not unaffordable only for poor countries, even wealthy countries might find it optimal to implement capital controls if they aim to keep a large amount of public expenditure. In short, the preservation of the welfare states might require a more frequent use of capital controls.