**1. Introduction**

The economic growth that Spain was experiencing after the mid-1990s abruptly ended in 2008 because of the global economic and financial crises. These exacerbated deindustrialization and globalization processes and favored inequality, which has grown in recent decades in both Spain and the majority of other capitalist countries [1]. In fact, this recession was partly caused by global financial markets that intended to maximize short-term benefits by investing in a secondary accumulation market linked to urban space production. These massive financial transactions targeted housing markets and produced a real estate bubble that, when it burst, triggered an economic recession in Spain, with the public and private debt crisis being another component. This observed urban basis of the economic crisis explains why the most negative effects were concentrated in large cities, reflecting the vulnerability of urban spaces [2].

This economic recession also affected international migration, Spain's main driver of population and urban growth, at the beginning of the 21st century. The previous highly positive migratory growth became negative [3], return flows slightly increased, and the number of young Spaniards moving to other European countries also rose. In addition, the economic crisis had an impact on residential mobility by reducing suburbanization flows [4,5] and increasing the attractiveness of urban cores [6,7].

**Citation:** Gil-Alonso, F.; López-Villanueva, C.; Bayona-i-Carrasco, J.; Pujadas, I. Towards an Even More Spatially Diversified City? New Metropolitan Population Trends in the Post-Economic Crisis Period. *Urban Sci.* **2021**, *5*, 41. https://doi.org/ 10.3390/urbansci5020041

Academic Editor: David Plane

Received: 1 March 2021 Accepted: 4 May 2021 Published: 14 May 2021

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The literature on the effects of the economic expansion and crisis on residential flows and urban dynamics extensively covers the Spanish context [4,5,8–10], particularly its two main urban regions, Madrid and Barcelona [11–17]. However, few studies have analyzed the consequences of the post-crisis economic recovery on urban dynamics.

Indeed, in 2014, the country started to show signs of economic recovery [18]. Economic activity and employment levels progressively rose, which had an impact on the real estate market [19]. Simultaneously, residential mobility levels seemed to recover while socio-residential strategies began to diversify [20], subsequently transforming interactions between intra-metropolitan spaces [21].

Thus, together with changes in the economic cycle, Spanish urban areas shifted from unprecedented population growth to stagnation and once again, more recently, to a new population growth phase that abruptly ended due to the impact of the COVID-19 pandemic. Still a scarcely studied period, this brief recovery phase between around 2014 and March 2020, the period studied herein, seems to have its own specificities. Residential mobility flows did not regain their pre-economic crisis characteristics, becoming more unstable, complex, and fragmentary [22]. This means that the direction of movement, migrants' reasons for moving, their socio-economic categories, and their ages all diversified, as did their impacts on Spanish urban cores and rings.

Therefore, our primary hypothesis is that, during the post-crisis period, Spanish urban areas experienced a great diversity of situations regarding the population growth of their cores and rings and that of whole metropolises. In other words, some city cores grew more than their peripheries, while, in other cases, suburbanization prevailed. At the same time, although the metropolitan population as a whole rose (again) in some areas, it continued to decline in others, as in the previous crisis period. Analyzing the population growth in Spanish urban areas while establishing a typology based on the increase and decline in core and peripheral populations, both in the economic crisis and post-crisis phases, is the first aim of this paper.

A secondary objective is to study the population growth and decline in the municipalities of the five largest Spanish metropolises for the same two four-year periods. Whereas the first part of the paper focuses on whether population change was diversifying among Spanish metropolitan areas in the post-crisis period, the second part analyzes whether this population growth heterogeneity increased within them.
