Pre-print, Working paper: We revisit the standard theoretical model of tax competition to consider imperfect mobility of both capital and labor. We show that the mobility of one factor affects the taxation of both factors, and that the "race-to-the-bottom" narrative (with burden shifting) applies essentially to capital-exporting countries. We validate our predictions using a panel of 29 OECD countries over the period 1997-2017. The quantitative contribution of rising capital mobility to the decline of corporate income tax rates over our sample period is nonetheless less than that of population ageing.