In many social outcomes, such as crime Sweden outperforms the US. An important question is whether this is due to Swedish welfare state policies, or due to demographic and cultural factors. Would the United States achieve the same outcomes with Swedish policies, or different outcomes due to American demographics and cultural factors?
In order to answer this immigrant outcomes is an useful indicator. Let us look at crime.
Sweden refuses to report the incarceration rate of immigrants. They do however report the incarceration rate of foreign citizens (people who don't have Swedish passports, not dual citizens). Immigrants who have gotten Swedish citizenship (56% of the foreign born 2008) will be counted as Swedes.
This measure will both underestimate and overestimate crime. It will overestimate crime if immigrants who have not yet become citizens are more criminal than other immigrants. It underestimates crime because the higher crime rate of immigrants that have become citizens are baked into the Swedish figures (also sometimes serious crime leads to deportation).
In the latest available year foreign nationals constituted 6% of the Swedish population and 29% of the prison population. Foreigners are thus 6.2 times as likely to be incarcerated than Swedes, or 520% higher incarceration rate.
The over-representation is even higher for middle eastern citizens, who are 6.6 as likely as Swedish citizens to be in prison.
Lastly African citizens are 10.9 times as likely as Swedish citizens to be in prison.
Swedish citizens have an incarceration rate of 45 per 100.000.
African citizens in Sweden in contrast have an incarceration rate of 490 per 100.000.
These people live under the Swedish welfare system. If the welfare system was the reason Swedes commit so little crime, it should have affected the immigrants similarly. Clearly it has not. My conclusion is that demography is as important or even more important than policy in explaining Swedish crime rates.