Caso 3: Se˜ nal de voz a trav´ es de un canal HDSL

The Chicago School and the ecologist en general have always displayed a more applied orientation which gave birth to a broad methodology aimed at explaining their main concern: the socio urban differentiation.

From the 40’s the efforts to realise a macro theory about the urban area went on decreasing. On the hand, the methodological work focused on explaining the inequalities gained in fame and extend, and this till our days (Lavia, 1995). The indices provided by Duncan and Duncan (1955), have served to realize huge part of the investigation about segregation at the global level. In fact they have been unanimously used in the analysis of the residential segregation till the 70’s, year in which many critics questioned the supposed uniformity of the urban areas and raised the problems related to of measuring the differentiation through incomes. Due to that there has been a period during which different school contributed to updating and developing the new rates that included other dimensions of the urban phenomenon, dimension that would be gathered in one of the most famous Works on that discipline “The Dimensions of Residential Segregation” co-written by Douglas Massey and Nancy Denton (1988). The two authors suggest 5 dimensions which take into account various indicators: evenness, exposure, centralization and clustering. If combined, these dimensions would give a multidimensional image of the residential segregation. The following table presents the indices used in this work in explaining each dimension, giving details about its formula, values and source.

Table 3.1 Indicators used for each dimension

DIMENSION INDICATOR FORMULA SOURCE RATE

EVENNESS

Index of

dissimilarity Ducan, 1955 Ducan and 0-1 EXPOSURE Index of

corrected

92 Index of

interaction Bell, 1954 0-1

CONCENTRATION Index Delta

Massey and Denton, 1988 0-1 CLUSTERING or GROUPING Index absolute grouping Massey and Denton, 1988 0-1 Index of medium closeness Massey and Denton, 1988 0-∞ CENTRALIZATION Proportion of people residing in the centre of the city Massey and Denton, 1988 0-1 Source: Compiled by author from Ducan and Ducan (1955), Bell (1954) and Massey and

Denton (1988) 3.2.1.1 Evenness.

Evenness is used in the case of two groups being unequally distributed in the same urban area. Understood so, a group is said to be segregated when it is unequally or unevenly distributed between given zones or areas of a city. For example and in absence of segregation, if a group represents the 10% of a population, the spatial distribution of such group in the different sections of the city must be of 10%. must reside 10% of such group in the different sections of the city. The rates or grade of segregation differ from a group to another, this makes it impossible to get a result based on the general percentage.

The most used indicator in measuring evenness is the Segregation Index or Dissimilarity Index. Dentro de los indicadores posibles para medir la igualdad, uno de los más célebres es el Segregation Index (IS). It is used to measure the differentiation between the minority group (X) and the proportion of the rest of the population in each section of the city. Another indicator in this same dimension and probably the most used is the Dissimilarity Index , which has same characteristics as the IS. In this case, the method used is to compare proportions of two groups at the same time and not of a group with respects others. In this same case, the index varies between 0 and 1, being 0 the absence of segregation and 1 the result of total segregation. It is interpreted using percentages in order to make visible the percentage of people that would have to change residential area in order to get to a situation of evenness.

(3.1) As in the previous case, x represents the minority group residing in the i section of the city and X refers to the minority group in the municipality as a whole (3.1). In the same line, y is the minority group in the section i and Y the majority group at the level of the municipality.

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This last index is applied into the 5th chapter to this work, “Residential Differentiation in the BMA” where it is used to measure the unequal settlement of the immigrant population in the BMA – Western Europe (UE15), Eastern Europe (UE28), Sub Saharan, The Maghreb, Latin America, China and Rest of Asia- and the main nationalities–Bolivia, Romania, Morocco, Paraguay, China, Senegal, Argelia, Nigeria, Pakistan. In the elaboration of this work we used data of the census of 2008 and 2015. That allowed to compare the current data to those of the years preceding the economic crisis and to establish possible tendencies. The same index has been used to analyse the residential differentiation of the main nationalities in the principal municipalities of the BMA (Barakaldo, Bilbao and Getxo).

3.2.1.2 Exposure.

As in the previous case, this index also requires information on the census. It is characterized by the concept of potential contact. It could be defined as the possibility of interaction between members of the same group or different groups. It is also one of the most measured dimensions due to its complementarity with the ID and its facility in accessing the census data, “Rather than measuring segregation as departure from abstract ideal of «evenness», exposure indices attempt to measure the experience of segregation as felt by average minority or majority member” (Massey and Denton, 1988). This dimension is composed mainly of two indices: the index of isolation and that of interaction.

The Isolation index (3.2) measure the probability there is for a member of a given group to have interactions with another member of his or her group. The index varies from 0 to 1, the maximum value means that the group is completely isolated in the special units of the urban space.

(3.2) In the formula (3.3), x represents the minority group in the section i and X refers to the minority group at the level of the municipality. In the same optic, y is the majority group of the section i and Y represents the majority group in the whole municipality. The n is used to represent the number of units (sections). Sometimes we also use the Corrected Isolation Index (Eta2)_{, which serves to adjust the different proportion with}

regards the whole population and where P refers to all the inhabitants:

(3.3) There exist a complementarity between this index and the Interaction Index (xPy) which contrary to the previous one measures the possibility of contact with a member of the majority group (nationals) in the same unit. Although the indices are complementary, they serve to measure different questions. The El Eta2 _{is based on the} existence of possible concentrations and the xPy takes into account the type of zone in which the interaction is produced (existence of more of less locals). The Interaction

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Index moves on a scale of 0 to 1, where its closeness to 1 means more possibility of interaction, meaning that the probability to interact with the locals is higher.

(3.4) As in the previous case, x represents the minority group of the section i and X refers to the minority group in the municipality (3.4). In the same line, y refers to the majority group of the section i and Y represents the majority population at the level of the municipality.

Both indices are applied in the chapter 5 where the date of the census of the years 2008 and 2015 are used for its elaboration differentiating the main areas of settlements by nationalities – Western Europe (UE15), Eastern Europe (UE28), Sub Saharan, The Maghreb, Latin America, China and rest of Asia- and the main nationalities–Bolivia, Romania, Morocco, Paraguay, China, Senegal, Argelia, Nigeria, Pakistan- when it comes to the BMA. The same analysis of exposure has served to analyse the residential differentiation of the main nationalities in the principal municipalities in Barakaldo, Bilbao and Getxo

3.2.1.3 Concentration.

This index and those that follow, require geographical censual data since they take into account spaces and distances. Concentration refers to the average space occupied by a minority group in the urban territory. The groups that occupy a small part of the urban space would experience a residential concentration. The small the residential space is, the more concentrated would the group be, thus more segregation it would experience. Some authors indicate that the segregated minorities occupy small areas of the urban territory, for that reason it segregation is related to its density “This observation stems from the fact that residential discrimination has traditionally restricted minorities to a small number of neighbourhoods that together comprise a small share of the urban environment” (Massey and Denton, 1988).

The most used index in this dimension is the Delta Index (DEL); it contemplates the difference of proportions between population and share in each section. It could be understood as the percentage of group X which has to change its area of residence in order to reach the same density in the whole city (Martori, Hoverg y Surinach, 2006).

(3.5) In the formula 3.5, A represents the space of the municipality and a the section i. X is the whole population and x the population residing in the section i. This index varies from 0 to 1. Its closeness to 1 indicates more concentration, resulting thus in more segregation.

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This index as well as all those requiring geographical information has been produced using the free multiplatform Geo-Segregation Analyzer (Apparicio and al., 2012), developed in the University of Montreal by Apparicio and Petketitch and translated into Spanish by Joan Carles Martori. Its elaboration has been made possible by using the census date of the years 2008 and 2015 and the digital cartography available on the webpage of the National Institute of Statistics.

It would be applied to the metropolitan area taking into account the main areas of settlements and to the Bilbao municipality considering the settlement zones of the most relevant nationalities.

3.2.1.5 Centralization

Although related to concentration this dimension considers it from it different aspect. These indicators measure the proximity of a group to the city centre. The presence of minority group in the centre of cities has originally been associated to high levels of segregation taking into account the situation of the minority Afro-American collective in many cities of the United States. However, “the situation is different in Europe and the use of the index is reduced to localizing the immigrant population in the urban space” (Martori, Hoverg and Surinach, 2006:4).

A very simple and most used index is the PCC which calculates the proportion of a group residing in the centre of the city where in our case the Xcc represents the number of a population X that lives in the central zone.

(3.6) This index requiring also geographical information has been elaborated for the years 2008 and 2015 using the Geo-Segregation Analyzer application (Apparicio and al., 2012). In this case the index, in order to serve, it requires a unique central unit that could be clearly identified. For that reason this analysis could not apply to the BMA, which is in fact a polycentric area. Nevertheless it could be applied to Bilbao capital and to the nationalities with more relevance in the years 2008 and 2015.

For this indicator it is needed to establish an area to be called the centre of the city. This study consider Abando as the centre of the Bilbao city following what has been originally idea which stated that the financial and commercial district would be considered as the centre of the city (Checa, 2006). A part from that Abando has a centric geographical position being located at the very centre of Bilbao. However, this selection could influence the interpretation of the index. If as the index indicates, the major concentration of immigrants is understood as segregation, in the case of Bilbao, Abando is rather characterized by a big presence of people with higher incomes and in facts in ecological terms, this district is defined as the CBD and is composed of dominant sections with referring the class struggle (Olabuenaga, 1982). So, the groups with a major presence in the centre would be less segregated or would at least be characterized by a better socioeconomic position.

96 3.2.1.6 Grouping or Clustering

This last dimension of residential segregation depicts the degree of grouping (physical) of two minority groups adjoin one another “While prior dimensions have dealt with the distribution of minority and majority members among areal units, or with the distribution minority areas relative to some fixed central point, clustering concerns the distribution of minority areas with respect to each other” (Massey y Denton, 1988). Grouping is created while a group of people are closely packed. This in turn gives way to segregation. In one Word a high degree of clustering implies a residential structure where the minority groups are contiguously or closely packed creating a kind of ethnical enclave inside the city.

Geographers have long studied this dimension which developed the Absolute Index Clustering in the urban space. It has to do with a complex formula when it comes to its execution and getting the data for its use. That is the reason why it is not often used in the analysis of residential segregation.

(3.7) Here too and as it the case it the previous cases (3.7), the x refer to the minority group residing in the section i or j. The t in this case would indicate the whole population of the unit called j. The Cij, refer to the original cell that connects the units i and j. Its value goes from 0 to a maximum which never reaches 1.

In order to complement the previous dimension, the indicators of the average distance between the units allow us to amplify the spatial information taking into account not only their contiguity but also the average distance between the members of the same group through indicators such the Average Proximity Index. This formula (3.8) that varies between 0 and ∞, shows the clustering of the groups en the urban space making an estimation the average distance separating members of the same group.

(3.8) These two indices are combined and applies in the chapter 5 where the differences between the settlement spaces of the nationals and people of immigrant background at the level of Bilbao i the years 2018 and 2015 are clearly seen. The elaboration of this indices was based on the use of the Geo-Segregation Analyzer application (Apparicio and al., 2012), the cartography of the NIS and the local census during the pre-economic crisis of 2008 (pre economic crisis period) and 2015.

3.2.1.6 The ratio of localization

A part from the previous one and although not being considered a real index of segregation, the ratio of localization is very useful to identify spatial units en the

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metropolitan area, units which could be underrepresented (QL<1) or rather overrepresented (QL>1). This ratio or coefficient makes it possible to map the spatial distribution of a group in the territory (Aparicio and al., 2014). It is a formula that allows us to determine the degree of concentration of a group in a unit. So the ratio serves to analyse the number of people from a specific group in comparison to the total population of an area. Doing so, we determine the degree of concentration taking into account not only the specific collective but also the whole population residing in the area.

(3.9) If we consider an area where X refers to the minority group (in one section or in general) and T, the whole population (in one section or in general), ratios which value are around 1 indicate that the number of immigrants living in a specific area is equal to their number in the whole city (3.9). The more the ratio goes above 1 in number, the more overrepresented is a group of people. But when the ratio is closer to 0 that indicates the group is underrepresented in the considered units.

This ratio is used in the chapter 5 as a complement in serving to localize the indices in the metropolitan area. With the data gathered through the ratio and using the data of the census at the level of the municipality in the years 2008/2015, we have been able to elaborate plans or graphic illustrations using the Mapinfo programme.