See also welfare state/fiscal burden objection, fiscal burden hypothesis, and contraction of welfare state.

The expansion of welfare state concern is a concern voiced by some people about open borders and more generally about liberal migration policies, particularly those who support or want to expand the welfare state provisions of the status quo in the immigrant-receiving countries. The concern is about how certain types of migration flows lead to an expansion of the welfare state, both as a fraction of GDP and in terms of qualitative description of welfare benefits available. Explicitly, the following are argued:

• Arithmetic effect: With a non-selective migration policy, migrants are more likely than natives to make use of certain welfare benefits, and more likely to create a net fiscal burden on the immigrant-receiving country. Thus, expanding non-selective migration would lead to an increase in the size of the welfare state relative to GDP.
• Policy effect: This is a political externalities arguments. It has been argued that migrants are more likely to support epxansion of welfare benefits. This may be because they are more likely to benefit from such policies (i.e., they are voting instrumentally) and/or because they have ideological commitments to the welfare state (for instance, they are replicating their home country policies). One plausible explanation for how such an effect might operate is that the migrants may be explicitly selected to support welfare state policies due to the welfare magnet hypothesis. On this view, expanding the welfare state attracts migrants who benefit from and like it, and these people vote for an even more expanded welfare state, leading to an ever-expanding welfare state.