Polycentric development and local fertility in metropolitan regions. An empirical analysis for Barcelona, Spain

The present study verifies if spatial variability in local fertility reflects the shift from a monocentric dense settlement model towards a polycentric metropolis organised in central cores and subcentral locations. The spatial distribution of a crude birth rate in Barcelona's province was investigated for a long time span (1975–2018), identifying distinctive trends within five concentric rings around Barcelona at four subperiods (1975–1985, 1986–1996, 1997–2007 and 2008–2018). Using multivariate exploratory statistics, local fertility rates were correlated with background indicators delineating the socio-economic profile of each municipality in the study area. Fertility rates decreased with the distance from downward Barcelona and with population density. In the first time interval (1975–1985), fertility levels—higher in subcentral municipalities and peri-urban locations than in downtown Barcelona—were positively associated with urban growth. In the following two subperiods (1986–1996 and 1997–2007), the contribution of local fertility to urban growth decreased significantly, reaching the lowest-low figures at the end of the 1980s. In the most recent time interval (2008–2018), a moderate (and spatially heterogeneous) recovery of fertility rates was observed in subcentral locations. Demographic processes underlying Barcelona's expansion provide evidence in favour of a positive relationship between polycentric development and local fertility. Our article finally debates on the use of fertility indicators in the assessment of monocentric versus polycentric (metropolitan) growth in advanced economies.