%T How internal migration shapes the demographic fertility patterns of internal migrants in post- Franco Spain %X The aim of this research is to discover the fertility difference between Spanish internal migrants who move between regions and their peers who do not. The focus will be on the fertility gap over time by comparing several groups with a ten-year interval between them. In particular, the focus will be on several theories and their importance to the Spanish context. By comparing the different time intervals, an analysis will be used to show the significance of this difference. The main research question will be: What migrant fertility theory supports the Spanish context the best? To answer this question a quantitative analysis will be conducted. Data used for this research will be collected from the IPUMS microdata database, which compiles data from several sources. This paper adds to the existing field by combining the fertility hypothesis of migrants and applying it to a special low-fertility context. The findings indicated that while there is little evidence to support one theory over another in terms of the total number of children, the age at which migrants start to have children is higher than their non-migrating peers. This indicates a delay in fertility, or a disruption. The findings further suggest that over time more support for this disruption hypothesis being dominant exists, with more migrant groups displaying a higher age at first birth. %L theses_frw4450 %D 2024 %A Tom Havinga