In-work support through the tax-benefit system has proved to be an effective way of increasing the labor supply of lone mothers and first earners in couples in a number of OECD countries. At the same time, these instruments usually create negative employment incentives for secondary earners....

Given that young children are under the control of their parents, if the government has an interest in either the welfare or the productivity of the former, it has no option but to act through the latter. Parents are, in the ordinary sense of the word, the government’s agents. They are agents...