1. IntroductionMortality is an indicator of health and disease risk (Razum et al. 1998). Studying differences in mortality between migrant and minority groups and the majority population might improve our understanding of the underlying mechanism. Mortality data from migrant groups in Norway could provide us with important insights, as there is a scarcity of data from Nordic countries. Secondly, in contrast to other Nordic welfare societies like Sweden, which has a longer period of immigration, Norway has seen a rapid rise in the migrant population, from negligible a few decades ago to a substantial part of the population being foreign-born today (14%). In an international context, Norway thus has a short immigration history and a comparatively late aging of the immigrant population. Furthermore, immigrant flows have been relatively fragmented, resulting in fluctuating stocks of immigrants, varying over time. This has resulted in large heterogeneity in the immigrant pool. In the past decade a large proportion of migrants have originated from low-income and/or Eastern European countries (Statistics Norway 2016). Given the origins of recent migrants, it might be assumed they are disadvantaged compared to the host population and therefore have poorer health or, on the contrary, that their health potential is better.Besides being dynamic and heterogeneous, until recently the immigrant population has not been sufficiently numerous to warrant studies examining differences in Norwegian mortality. The Norwegian context is particularly interesting due to the country's egalitarian welfare policies, including freely available health care. Furthermore, social and gender equity policies have resulted in lower levels of inequality than elsewhere.1.1 The Norwegian settingThe immigrant population in Norway, comprising immigrants and their descendants, has gradually increased from 1% in the early 1970s to 15% today (Statistics Norway 2016). It is expected to continue to increase quite substantially over the coming years (Cappelen, Skjerpen, and Tonnessen 2015). Norway's immigration policy was fairly liberal post-World War II. In the 1950s, immigrants comprised around 1% of the population and were mostly from Sweden, followed by refugees from Eastern Europe and thereafter by labor immigrants from other parts of the world. The post-1975 freeze on labor migrants meant that majority of migrants to Norway thereafter were refugees from Asia, Africa, South America, and Eastern Europe. However, with the expansion of the European Union (EU) in 2004 there was a marked increase in labor immigration from new EU countries, particularly Poland and Lithuania. The history of migration to Norway shows that the reasons for migration have varied over time, thereby influencing the composition of the immigrant population in Norway. For the study period 1990- 2012, family reunification, employment, education, and refuge from conflict, political oppression, persecution, and natural disasters represented 39%, 31%, 6%, and 22% of the reasons for immigration, respectively.Over the past five years the immigrant population in Norway has increased by almost 50%, from 552,000 to 804,000 (Statistics Norway 2016). Norway's immigrant population is heterogeneous and migrants originate from 221 different countries with the largest groups coming from Poland, Sweden, Somalia, Lithuania, Pakistan, and Iraq. In 2014 the largest groups arrived from Poland, Lithuania, and Eritrea.Despite the dramatic rise in migration, Norway is not the first country of choice for many migrants. As was previously the case, most migrants prefer the UK, Germany, and/or Switzerland (IOM 2015). Norway has not been a colonial power and therefore has no migration from former colonies, as in the Netherlands and the UK. Furthermore, prior to finding oil in 1970 Norway was a relatively poor country, which, together with a cold, harsh climate, may have deterred migration. …