subcontracting, giving away new science to private firms etc. constitutes a new kind of "accumulation by dispossession" . Lewis in his Nobel prize winning Theory of Economic Growth and model of economic development argued the opposite – that the capitalist sector raises wages, drawing unproductive labour out of the non-capitalist sector, creating a self-sustaining process of economic development. Population growth. Marx failed to systematically theorize the impact of demographic effects on economic reproduction, except that he studied the reserve army of labour and criticized the "overpopulation" theories of Thomas Malthus. Malthus was anxious that population growth would outstrip the capacity of the economy to sustain all the new people. Marx replied that the very idea of "overpopulation" was an anti-human ideological fiction, since it really meant "overpopulation" only relative to the requirements of capital accumulation. If resources were appropriately allocated, there was enough for everybody to have a decent life. The real point was that capital could not achieve that goal. Capital accumulation necessitated a "relative surplus population", which tended to grow in size. Nevertheless, since population trends are not simply determined by economic factors, population movements can exert an important independent effect on economic reproduction. In China population growth has been curbed by deliberate government policy to restrict the number of births per couple, using birth control methods. Another aspect about which there is much controversy is the emigration of workers and refugee populations, whether they are an asset for, or a drain on, economic growth. Capitalists are generally in favor of the free international movement of capital, but they are much more cautious about freedom of movement for workers, depending on whether that movement is profitable to them or whether it is a cost or a political threat. Public finance. Marx did not analyze in any detail the effect of taxation and state expenditures on the reproduction process. In his time, state taxes and expenditures were comparatively small (5%–10% of gross product), but since that time they have risen to 30%–40% or more of gross product in many countries. They enable the state to intervene directly in the process of social and economic reproduction, and to alter its course within certain limits. Because of the size of state funds and the fact that taxes must be paid irrespective of productive performance, the state can borrow large sums and use them, together with legislation, to influence economic growth and