Introduction

1Several of the authors of reference in the field of urban studies (Brenner, 2010; Soja, 2011; Harvey, 1985; McFarlane, 2011; Amin & Thrift, 2002), coincide in their reading of urban and cityness, as a precarious and continuously restructuring results of the process of capital accumulation, rather than as a territorially delineable and empirically verifiable entity (Brenner, 2010). This unstable and changeable character of urban assemblages seems to be particularly visible in the current historical phase, marked by a plurality of crises at macro-regional and global scale (Tooze, 2018), which accelerate and multiply the changes in the pattern of the capital accumulation, making it necessary to constantly update the interpretative framework of the urban process.

2In the era of planetary urbanisation (Brenner & Schmid, 2014), urban processes disrupt traditional urban hierarchies, flatten the differences between urban and non-urban and between centre and periphery, and at the same time generate assemblages that transcend the mere areal dimension, however wide it may be (Brenner, 2004; Brenner & Schmid, 2014; Soja 2011). However, this homogenisation of the territory, both in terms of landscape, as well as lifestyles, is not matched by a flattening of socio-spatial inequalities, which on the contrary constitute a muster piece of what Bernardo Secchi has called the new urban question (Secchi, 2010). A renewed question linked not only by the expansion of the metropolitan territory, which, with Soja’s terminology, we can define post-metropolitan. But above all by a qualitative leap in the structuring of its internal dynamics characterised by the trans-scalarity of urban formation processes.

3The present article intends to contribute to the ongoing debate on the urban regionalisation emerging process, investigating in particular the links between regionalisation and socio-residential specialisation and critically analysing the relationship between both processes and the spatial-temporal coordinates within which they occur. It is within this exploratory horizon that the article analyses the processes of segregation that have fractured the post-metropolis of Milan during the decade since the outbreak of the 2008 economic-financial crisis, generating new patterns of concentration of economic capital and high-income population on a regional scale.

4The hypothesis is that taking this specific point of view, at the crossroads of urban regionalisation processes and the territorials’ effects of the economic crisis, can contribute to advancing our understanding of the effects of the process of planetary urban extension on the restructuring of patterns of socio-residential specialisation in contemporary urban regions.

Nexus between urban regionalization and socio-residential specialization

5The consequences of regionalisation processes on socio-territorial cohesion remain largely to be understood. Depending on the research, the case studied and the methodologies chosen, the urban regionalisation can be read as a process of explosion of the complexity of the city in the region (Lefebvre, 2003 [1974]) with a consequent increase in the social mix, land uses and functions (Soja, 2011; Balducci, Fedeli & Curci, 2017a) or it can be read as well as a risk of extreme specialisation and segregation of territories (Estèbe, 2008; Blanco & Nel·lo, 2018).

6The increase in complexity and social mix is made to descend, by a part of the literature, directly from the processes of planetary urbanisation and urban regionalisation (Lefebvre, 2003 [1974]; Soja 2011). In this perspective, the process of density convergence noted by Edward Soja (2011), is to be read as a progressive elimination of the differences between urban and suburban territories, which is accompanied by an increase in functional, social, morphological and topological heterogeneity of the entire regional territory. These processes produce a finer and more varied pattern, in which densities take on an “irregular and confused profile” (Soja, 2011) due to a selective intensification of specific portions of territory according to their relational properties rather than their physical proximity to urban centres (McFarlane, 2016).

7The analysis of these same relational dynamics, however, leads other scholars to opposite conclusions, such as the geographer Philippe Estèbe who reads the Ile de France region as a set of isolated places with high functional and socio-residential specialisation. These findings propose an urban regionalisation process in which the convergence between urban-rural and urban-suburban theorised and described since Lefebvre, instead of a “pulviscular” mixing, generates club territories (Estèbe, 2008) or clusters, characterised by a high degree of internal homogeneity. The resulting territorial organisation is characterised by high human and non-human flows that connect and sustain the different monofunctional territorial pieces, and by barriers, both material and immaterial (Secchi, 2013) that mark their alternation. Blanco and Nel·lo (2018) in their research on the Barcelona Metropolitan Region come to similar results, emphasising, moreover, how the economic crisis of 2008 has increased the separation of the population into residential supra-municipal clusters encompassed in the metropolitan space.

8On closer inspection, the two readings are in some ways compatible and complementary, if we assume that the urban implosion/explosion that has taken the urban process from the political city to overcoming of the critical zone, as described by Lefebvre (2003 [1974]), has generated a post-urban world (Haas & Westlund, 2018) in which the differences between urban and non-urban are thinned out, to the point of cancellation, (and the concept of urban as an object disappears (Farías, 2009)), and the planetary projection of “multiple and dissociated” (Lefebvre, 2003 [1974]) urban fragments has given rise to territories, functionally connected to the rest of the urban system, but internally homogeneous and externally differentiated from those adjacent and therefore segregated (Estèbe, 2008).

9The theorisation and the first empirical research on urban segregation is due to the school of human ecology developed at the University of Chicago in the early 20th century. Michael White (1983) defines segregation as the phenomenon of separation or distribution in space of the population according to its economic, social, phenotypic or cultural differences. Over the years, the scholars of the functionalist current have developed models of metropolitan segregation organised by concentric zones, sectors or multiple cores, refining their theorising on the basis of empirical studies on the major US metropolitan areas (Wirth, 1938; Timms, 1975; Park, 1915; Burgess, 1928; Mc Kenzy, 1924). After them, and sometimes in stark opposition, many authors have carried out empirical analyses of residential segregation in various contexts, both US and European (Tammaru, Marcińczak, van Ham & Musterd, 2015; Arbaci, 2008; Musterd & Ostendorf, 2005; Musterd, Marcińczak, van Ham & Tammaru, 2017; Massey & Denton, 1988; Sassen, 1991; Marcuse, 1989).

10What the different territories seem to have in common is the metropolitan dimension, which already clearly emerged in the 1950s and reached its peak in the 1980s, with what Massey (1996) called the urban poverty concentration, i.e. the process that took place, especially in the United States, of concentration of the racialised and low-income population in urban centres hyperghetto (Wacuant, 2001) and of dispersion of the middle class in the so-called suburbs, often belonging to other municipalities.

11Relating these dynamics to the state of contemporary urbanisation process, it is interesting to note that while the distinction between urban and sub-urban is blurred, administrative fragmentation has remained more or less unchanged since the 1980s until today. These administrative divisions, involving rules, resources, rights and obligations, form part of what is defined as urban. Edward Soja, in ’Seeking Spatial Justice’ (2010), states that space is not a “vacuum”, but on the contrary, a “full” of policies, ideologies and other forces that shape life. These, following McFarlane, are to be considered components of a vast and dense set of interactions that enable and disable, alienate, exploit or inspire different forms of urban life (McFarlane, 2009).

12As introduced by the “neighbourhood institutional resource models” strand (Jencks & Mayer, 1990), differences in the quantity and quality of material resources and services between territories and populations are elements that can reproduce inequalities. Annette Hastings (2009a) introduces the concept of institutional rationing referring to the inequalities between social groups due to the unequal distribution of public resources linked to budgetary constraints, resource allocation choices, as well as to public spending review and changes in territorial redistribution mechanisms (Judge, 1978) often implemented in response to crises, both of the economic and political system.

13Since the outbreak of the 2008 economic crisis, new researches had returned to focus on neighbourhood effects generated by institutional determinants and, in particular, institutional rationing mechanisms. A relevant example, focused on territories close to the case study analysed in this article, is the triad of books “Barrios y crisis” (Blanco & Nel·lo, 2018), “Efecto barrio” (Nel·lo, 2021) and “Vidas segregadas” (Blanco & Gomà, 2022), which demonstrate, amongst other, the multiplier effects of inequalities generated by the mismatching between the residential pattern that reached a regional scale and the stability of administrative limits, which underlie the criteria for allocating resources distributed to municipalities to produce utilities for their residents (Donat & Nel·lo, 2017; Donat, 2021).

14Taking together the variegated literature presented so far, it is proposed to read the Milanese urban region as trans-scalar assemblage, not only of the profoundly diverse territories that compose it and the materialities and individuals present on them, but also of regulatory provisions such as administrative boundaries between different municipalities, of resource allocation choices at different scales, of the 2008 economic crisis and its effects on population’s income as well as of the numerous public spending reforms connected to it. As expounded by McFarlane, the reading of the urban as assemblage facilitates the understanding of urban inequalities as the product of distinct space-temporal processes; that of "public policies, capital accumulation, everyday cultural practices" (McFarlane, 2011, p. 210) and so on, precariously and only temporarily held together by the action of the actors from time to time hegemonic, but always reassemblable through contestations and changes of power (Li, 2007).

15Through this reading, it is possible to deepen the relationship between regionalisation and socio-residential specialisation, highlighting how both are the result of heterogeneous and hetero-directed factors, produced by actors at different scales and highly unstable in character. Such a reading also emphasises the precariousness and temporariness of these processes and the forms in which they develop and are visible at any given time.

Methodology

16Starting from the literature explored in the previous section, this investigation analyses the process and pattern of concentration of capital, both private and public, led by the socio-residential specialization process, within some selected territories of the Milan urban region.

17The analysis is developed by the two specific objectives set out below:

18- Analyse the population’s distribution in Milan urban region according to its income and understand whether the degree of social-residential specialisation has increased during the 10 years since the outbreak of the economic crisis in 2008.

19- Check the relations between the social-residential specialisation observed in the first objective and the resources held by municipalities that compose the areas of analysis.

20The area of analysis corresponds to the limits of the Metropolitan City of Milan. These are administrative limits that correspond only in part with the geographies of the productive and reproductive organisation of the regional population. The research, in agreement with the numerous contributions generated since the Italian National Research Project (PRIN) Post-Metropolis (Balducci, Fedeli & Curci, 2017) recognises the impossibility of drawing areal limits capable of totally containing the urban region. Given this impossibility, the administrative limits of the Metropolitan City have been chosen with the aim of referring the analysis to a territory directly endowed with instruments of action that, albeit partial, can act by limiting the metropolitan gaps that this research analyses. The Metropolitan City of Milan is a supra-municipal local authority established in 2015 as a result of Law no. 56 of April 7, 2014, and Regional Law no. 92/2015. It replaced the provincial authority, inheriting its administrative boundaries, within which 133 municipalities are located, covering an area of 1,575 square kilometres. It is internally divided into Homogeneous Zones made up of several municipalities, some of which are further subdivided into Zones. Among its main functions are strategic planning, provincial territorial coordination planning, and transport planning.

21The data used for the income distribution analysis are derived from the database of personal income tax returns (IRPEF) made available to the public by the Finance Department of the Italian Ministry of Economy and Finance (MEF). The data collects the total income of taxpayers divided by municipality for each year from 2008 to 2018. For the Municipality of Milan only, IRPEF’s data divided into sub-zones according to the Postal Code (ZIP code) referring to the year 2015 were used in addition. Before the analysis operations, it was necessary to incorporate the effects of inflation on income by linking the real value of the euro to the national consumer price index (NIC) compiled by ISTAT (Italian Statistics Institute).

22With the aim of producing a finer picture of socio-residential specialisation, some socio-demographic data at the census sections scale were added to the municipal scale data referring to incomes, referring to four different spheres of vulnerability: employment, welfare, housing and social spheres. The variables were assembled into a Synthetic Index of Residential Segregation (SIRS), similar to the one employed by Blanco and Nel·lo (2018), elaborated for more than 15 thousand census sections that make up the analysis area.

23The variables employed come from 2011 Census data:

24- Employment sphere: Total unemployed resident population aged >= 15 years seeking new employment.

25- Welfare sphere: Resident population with primary school diploma (without other diplomas).

26- Housing sphere: average m² of houses occupied by at least one resident (Average area = total area/number of dwellings = a /B).

27- Socio-demographic sphere: Population resident in Italy with nationality of countries located in Africa, America, Asia, Oceania or stateless.

28The SIRS measures segregation by calculating, for each variable, the difference between the standard deviation of the variable and the standard deviation of the normal distribution of the same variable. In calculating the normal distribution, for maximum adherence to the characteristics of the variable, which do not contain negative values, was used the approximate Poisson formula, whose characteristic parameter is the expression of both the mean value and the variability of the distribution.

29To fulfil the second objective, were used data of the balance sheets of the 133 municipalities of the Milan Metropolitan City derived from different sources: 1) from the database managed by the Openpolis Foundation, which collects data about the local administrations’ financial situation; 2) from dates managed by the SOSE (Soluzioni per il Sistema Economico) assets of Bank of Italy and MEF; 3) direct consultation of the municipalities’ balance sheets.

Results

Income concentration and socio-residential specialisation

30The Metropolitan City area in 2018 comprises more than 3.250 million residents, the average income per resident stands at EUR 21,342.28. Dividing the municipalities into deciles according to the average per capita income of their residents, a large gap emerges between the municipalities in the tenth decile and the rest of the municipalities, so that while the municipalities belonging to the first decile have a per capita income of 47% of those in the tenth decile, the differences narrow sharply compared to the ninth decile, of which they have 77.4% of the income. Between the first and ninth deciles, per capita income varies by EUR 4,721.61 per year, while between the ninth and tenth deciles it varies by EUR 13,520.82.

31The results of the SIRS allow us to deepen the data just exposed. The index shows that 14.1% of the population residing in the municipalities belonging to the first decile suffers a situation of vulnerability linked to more than one of the different spheres of reproduction of inequality that make up the index. The population in the same situation residing in the municipalities belonging to the tenth income decile corresponds to 1.7% of residents, if we exclude Milan. More than 63% of the socio-economically vulnerable population of the territory resides in the municipalities of the first three deciles, while the total population of the first three deciles only accounts for 28.3% of the Metropolitan City. Conversely, the tenth decile, alone, houses 46% of the wealthy metropolitan population, weighing only 12.9%. Together with the ninth decile, it accounts for 57.8% of the affluent population.

32The Gini index applied to the average per capita income of municipalities shows a marked increase over the decade, characterised by three phases. An initial increase, during the first four years, linked to the first signs of the crisis, which generate a tendency for incomes to fall, but which involves high income municipalities to a lesser extent and does not affect municipalities in the 10th decile. A second phase, between 2011 and 2013, in which the decrease in incomes involves all the municipalities in the region, leading to a decrease in the value of the index. A third phase, starting in 2014, in which incomes rise again, but at differential speeds depending on the average per capita income of each municipality. The ninth and tenth deciles grow about twice as fast as the others. In 2018, the Gini index is higher than in 2008, the population of the municipalities in the ninth and tenth deciles has increased its abstraction from the rest of the territory, being the only deciles to have had a positive performance during the decade.

33The spatial arrangement of social groups according to their income is well readable at the regional level. Although the pattern is complex and varied, the concentration of income is observed in four main areas of the urban region. First, the central districts of the Milan municipality, where the concentration of high-income households is highest. Income concentration extends from the regional capital to the municipalities in the eastern sector of the first ring, extending along the Martesana axis to Gessate. The western area of the Metropolitan City is characterised by a generalised medium-high income in which municipalities with a high concentration of income are located in the second ring, towards Magenta or in the north-west in Arese. The municipalities with the lowest per capita income are also arranged in space with relations of some interest. The north-west and south-west fringes of the Metropolitan City, unlike the average income of the first and second tier municipalities in the west of Milan, concentrate a significant share of municipalities with the lowest per capita income. Then there are other smaller clusters (Figure 3). Even for the low-income areas, the neighbourhoods still belonging to the municipality of Milan merge with the low-income neighbourhoods of the municipalities.

34Through the spatialisation of the SIRS, it emerges that the wealth and vulnerable segregated neighbourhoods correspond in good shape with the per capita income level of the municipalities in which they are located, except for those located in the capital’s periphery and in the most peripheral municipalities of the Metropolitan City.

35Comparing the data of 2018 with those of 2008, we observe how the crisis has acted on metropolitan inequalities by a) decreasing the average incomes of those territories that were already characterised by their economic vulnerability before the crisis and increasing the concentration of incomes in the municipalities of the affluent self-segregation, b) including into the vulnerable clusters of territories, municipalities that before the crisis were not yet considered as such, and c) bringing the economic conditions of residents of municipalities with medium-low and medium-high pre-crisis incomes closer.

36While the territories of economic prosperity in 2018 are roughly the same as in 2008, the existing low-income territories belonging to the western fringes of the post-metropolitan area are expanding. In the western periphery of the Metropolitan City, Abbiategrasso and the neighbouring territories reduce their incomes, consolidating as a low-income area, as does the band of low-income municipalities in the upper Milan area. In the first metropolitan ring, low-income areas in the south of Milan around Rozzano and in the north between Cologno and Cinisello Balsamo deepen their poverty and expand spatially.

Unequal reduction of municipalities’ budgets and neighbourhood effect

37In 2008 the revenue per capita was EUR 2,366.53 counting Milan and EUR 1,068.25 excluding it. The withdrawal period is concentrated between 2008 and 2014, reaching in 2014 to EUR 1,603.65 per inhabitant with Milan and EUR 877.83 without. The annual decrease (excluding Milan) was between 2.9% and 4.5%. On the other hand, the period from 2016 to 2018 marked an increase in per capita revenue (outside Milan). At a fixed euro value in 2008, revenues in 2018 are 29.3% lower than in 2008 in the Metropolitan City’s municipalities, while they remain about the same without considering Milan. If revenues had not decreased, around EUR 1,370 more per resident would have been earned during the decade without considering Milan and EUR 6,500 including it.

38Dividing the municipalities into deciles according to their per capita revenue, in 2018 the first decile counts with 29.6% of the resources that the municipalities in the tenth decile can count on, excluding the Municipality of Milan, 24.6% including the capital city. The same index in 2008 was 40% without taking Milan into account, while it was 18.6% including it. These data illustrate a high gap in term of revenue within the Metropolitan City, even greater than that generated by the concentration of incomes. On the other hand, they show the sharp decrease in revenue of the capital municipality. The Gini index applied to municipal revenues decreases until 2013, due to the generalized decrease in local administration revenues, and increases again in the years between 2014 and 2017, exceeding 2008 levels.

39Returning to dividing the municipalities by per capita income decile and observing the overall revenue that the municipalities of each decile have available, it emerges that those of the first decile in 2018 accounted for EUR 975.80 per resident, while the municipalities of the tenth decile, excluding Milan, count with EUR 1,318.78, or 26% more. The impact of the crisis on municipal resources acts as a multiplier of the income gaps between the different territories of the region. At a fixed euro value in 2008, the resources of the local authorities belonging to the first decile decrease by 16% during the decadal, while those of the municipalities in the tenth decile, by only 4%. Moreover, those municipalities that had a low per capita income in 2008 are the ones that decreased their revenues much more sharply during the economic crisis than municipalities with 2008’s high incomes. The municipalities belonged to the first three deciles in 2008, in 2018 have revenue budgets that are 10.6%, 5.8% and 11.3% lower than in 2008, respectively, while the top three deciles only 1.5%, 3.1% and 3.1%, respectively. This reflects the asynchrony of the impacts of the crisis on municipal authorities’ resources and residents’ incomes, in a context of progressive regionalisation of the population’s life geographies.

Pattern of socio-residential differentiation between unequal distribution of income and public resources

40Adding up the results from the previous two paragraphs, it emerges that the inhabitants of the municipalities of the 10% least well-off, in 2018 possess about 4% less of the resources, summing private resources from income and those available to municipalities, that they would have if the resources were distributed equally among the inhabitants of the urban region. In contrast, the wealthiest 10% possess almost 6% more (Figure 6).

41Finally, the map corresponding to Figure 7, summarising the work done, shows how the post-crisis Metropolitan City territory is characterised by a concentration of resources in some “pouches of well-being” almost always resulting from the aggregation of several municipalities homogeneous by socio-economic conditions, in which almost all affluent auto-segregation neighbourhoods (data from SISR) are located. And how, conversely, the “gaps”, left by the location choices of the affluent population, generate areas of increasing economic vulnerability.

Conclusions

42This article explored the pattern of socio-residential differentiation in the territory of the Metropolitan City of Milan at the intersection between the neighbourhood effects generated by the overlap between the regionalised residential geographies and the stability of the municipal limits and the advent of the 2008 economic crisis, which acted both on the productive and redistributive sphere. The analysis contributes to the understanding of the characteristics of the urban process currently taking place in the urban region by showing the mechanisms of the unequal accumulation of capital within the territory, setting them in the space-time of the ten years following the outbreak of the crisis.

43In the case of Milan Metropolitan City the progressive urban regionalisation, which has projected residential functions outside the regional core since the 1950s (Gabellini, Morandi & Vidulli, 1980; Lanzani, Marini & Boeri, 1993), has cancelled the differences between urban and sub-urban, without however leading to a social mixing of the region, but rather to a progressive segregation and specialisation of territories, aggravated by the economic crisis of 2008, which has acted path-dependent on the basis of longer-standing geo-historical patterns resulting from the different economic-territorial phases that have touched the Milanese regional assemblage.

44The cross-reading of the income analysis and the SIRS shows a coincidence between the segregated census sections and the average income per capita of the municipalities in which they are located. This confirms a reading of the territory composed of large “pieces” that tend to uniform internally and differentiate externally, similar to those baptised by Philippe Estèbe in his analysis of the Île-de-France as club territories (Estèbe, 2008). Exception are the territories on the periphery of the metropolitan core, characterised by a greater degree of heterogeneity, in which the granularity of the pattern of socio-residential differentiation is finer and more similar to the post-metropolitan area as usually described, i.e. as a mix of uses, functions and populations (Soja, 2011).

45The article also showed how the miss-matching between the pattern of residential differentiation and the administrative limits, loaded with regulations, resources, rights and obligations, acts as a multiplier effect of socio-economic inequalities, further diminishing the socio-territorial cohesion of the urban region. In this dynamic, the economic crisis has acted both on the productive sphere, increasing the concentration of income in the territories, and on the redistributive capacity of municipal authorities.

46In conclusion, the reading of the Milanese urban region as an unstable assemblage proved useful in demonstrating how the mismatch between processes produced on distinct space-temporal scales led, in the case analysed, to an increase in socio-spatial inequalities within the assemblage. It is fundamental to renew the question of how to structure policies capable of stopping the ongoing segregation processes and the consequent effects of reproduction and increase of inequalities. Which actors, with which resources and through which mechanisms, are questions that this article does not answer and that require further study, with a renewed awareness of the risks linked to the growing socio-spatial fragmentation of the Milan regional assemblage.