Dramatic changes in the ethnic composition of countries in the last decades have sparked new interest among social scientists in studying and uncovering the role of ethnic diversity on social, political and economic outcomes. Yet, most ethnic fractionalization indices used by scholars to study these effects treat ethnic heterogeneity as time-invariant, thus concealing its long-term effects. However, failing to take into account historical developments in ethnic composition might seriously hinder our understanding of their effects on social, economic, and political outcomes. This paper introduces a new dataset containing an annual ethnic fractionalization index for 162 countries across all continents in the period of 1945-2013. The Historical Index of Ethnic Fractionalization (HIEF) dataset is a natural extension of previous ethnic fractionalization indices. It offers the opportunity to study the effects of ethnic fractionalization across countries and over time. The article concludes by offering some preliminary descriptive analysis of patterns of change in ethnic fractionalization over time.

Attitudes toward immigration have attracted much scholarly interest and fuelled extensive empirical research in recent years. Many different hypotheses have been proposed to explain individual and contextual differences in attitudes towards immigration. However, it has become difficult to align all of the evidence that the literature has produce so far. The present article contributes to the systematization of political science empirical research on public attitudes toward immigration in the last decade. Using a simplified combined-tests technique, this paper identifies the micro-as well as macro-level factors that are consistently linked to attitudes toward immigration. It reports findings from a meta-analysis of the determinants of general attitudes toward immigration in published articles in thirty highly ranked peer-reviewed political science journals for the years 2009 -2019. The results warrant a summary of factors affecting attitudes to immigration in a systematic, measurable and rigorous manner.

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