Disentangling the quantum and tempo of immigrant fertility

Migrant fertility has become an increasingly prominent explanation for recent fertility change. Immigrant Total Fertility Rates (TFRs) are consistently higher than native TFRs in the majority of European countries (Sobotka, 2008). However, research has cast doubt on the use of tempo-distorted measures of fertility for evaluating the contribution of immigrants to aggregate fertility (Toulemon, 2004, 2006). Furthermore, previous research has almost exclusively analysed incomplete or partially completed fertility profiles, an approach which provides minimal insight into the absolute impact of immigrant fertility. Considering the UK, this research uses survey estimation and count regression techniques to disentangle tempo variation from the quantum of immigrant fertility. This approach is crucial for testing migrant fertility hypotheses because migration is known to influence the timing of childbearing (e.g. Andersson, 2004). The results support several hypotheses, with evidence of disruption followed by elevated fertility, particularly for recent cohorts of women arriving after age 25. This may be explained by selection, anticipation, or adaptation. Furthermore, the results show variation in the underlying fertility profiles of different immigrant groups by country of origin, and provide new insight into the links between quantum and tempo for immigrants to the UK. After exploring these results in detail, this paper discusses the benefits of this approach for understanding migrant fertility and informing population projections.