Diversity in a Globalized World

Lecture 4: Who Lives Next to Whom

Bogdan G. Popescu
bgpopescu@tec.mx

Tecnológico de Monterrey

Where the week has been

  • Monday: a shock landed on particular places, not on a country
  • Tuesday: those same places voted differently afterwards
  • Wednesday: some people left — and the money came back
  • Today: the people who stayed, and the people who arrived

Same country, sometimes the same city — and still apart. That is the question the course title has been circling all week.

Three numbers

  • 7.4 million speak an indigenous language — 5.8%. Almost nine in ten of them speak Spanish as well
  • 2.6 million identify as Afro-Mexican — 2%
  • 371 municipios are majority indigenous-speaking; 1,047 are under 1%

The country is diverse. Most of the places in it are not.

Source: INEGI, Censo de Población y Vivienda 2020 (press release 430/22). A speaker is anyone aged 3 or over who reports speaking an indigenous language, whether or not they also speak Spanish: 6.4 million (87.2%) do, 866 thousand (11.8%) do not. Shares here divide by total population; INEGI’s published 6.1% divides by the population aged 3 and over.

Those three numbers, on a map

Figure 1

The dark municipios are the 371. Oaxaca alone holds 203 of them.

Learning objectives

  • Say where difference sits in Mexico — not just how much of it there is
  • Turn “this city is divided” into a number, and know what that number misses
  • Explain how a city can divide itself with nobody intending it
  • Tell that apart from discrimination — and know how discrimination is tested
  • Say whether living closer together actually reduces prejudice

Diversity is not spread evenly

Figure 2

A second map, a different geography

Figure 3

Source: INEGI, Perfil sociodemográfico de la población afrodescendiente en México (Censo 2020). Shares are of each state’s own population, which rewards small states: Baja California Sur’s 3.3% is 26,330 people, Veracruz’s 2.7% is 215,435. By headcount the largest populations are Guerrero (303,923), Estado de México (296,264) and Veracruz. Self-identification is volatile — the national count rose from 1.38 million (1.2%) in the 2015 Intercensal to 2.58 million (2.0%) in 2020 — and INEGI notes that in some states, such as Ciudad de México and Colima, the population is explained by migration rather than historical settlement. In Yucatán, 26.6% of those identifying as Afro-descendant also speak an indigenous language, above the state’s own 23.7%.

Three words that are not the same

Same 400 people, same 25% blue in each. Three different questions.

Figure 4

The first two compare places. Only the third looks inside one.

The same three words, in Mexico

The question What it looks like here
Composition how many, in this place? a municipio is 30% indigenous-speaking
Concentration which places? most speakers live in a few southern states
Segregation which neighbourhoods, inside one place? in one city, the groups share no neighbourhood

Only the first is diversity — how much difference a place holds. The other two are geography: where that difference sits.

Almost everything today measures the first two. Only the third is segregation — and it needs smaller units than a municipio.

Concentration, in one number

  • Oaxaca is 30% indigenous-speaking; Chiapas 26%; Yucatán 23%
  • Guerrero is 8.6% Afro-Mexican, the highest in the country
  • Two thirds of all speakers live in one tenth of municipios

A national average of 5.8% describes almost nobody’s street.

So what?

  • Mexico is diverse as a country
  • Most Mexicans live somewhere that is not
  • “How much difference?” and “who meets it?” are different questions

Which raises the question of whether where you live also shapes how you live.

The two maps look alike

Figure 5

What this does and does not say

  • The pattern is strong and it is real
  • It does not tell us why
  • Remote municipios are poorer, and also more indigenous

Geography, history and discrimination all predict the same map. A correlation cannot separate them — which is why the rest of the lecture takes the mechanisms one at a time.

So what?

  • Where a group lives is bound up with how it lives
  • At this scale we compare whole municipios
  • The interesting sorting happens at a much smaller scale

So let us take one city apart.

Monterrey, thirteen municipios

Same question, different cleavage: this metro is only 0.4% to 4% indigenous-speaking, so the difference you can see inside it is class.

Figure 6

The same city, ranked

Figure 7

Putting a number on unevenness

The index of dissimilarity asks one question: what share of one group would have to move for the two groups to be spread evenly across the city?

Figure 8

Both sit near the left end. A five-fold gap between two municipios is not yet a divided city.

Which city is more segregated?

Two cities, four neighbourhoods. Same 200 blue and 200 green in each.

Figure 9

Why City 2?

  • The middle two neighbourhoods are identical in both cities
  • The cities differ only at the ends — and City 2 pushed those all the way
  • One neighbourhood is all blue, the other all green

To even City 2 out, 60% of its blue residents would have to move. In City 1, 40%. That is the index: 0.60 against 0.40.

Is Monterrey unusual?

Figure 10

No. Every large metro has a gap like this.

But read it carefully: this is a gap between municipios. It says the groups are sorted. It does not say how mixed any one of them is — that is the third word.

One honest caveat

In the Valle de México the gap runs from 8% to 76%. Monterrey’s runs from 5% to 28%. Tijuana’s is only 10 points wide.

But these compare municipios, and Monterrey municipio alone holds over a million people.

Real segregation happens street by street. Every number here is a floor, not a ceiling. Say so when you report one.

You have met this problem all week: Monday’s commuting zones, Wednesday’s whole-city comparison for Mariel. Each time, the unit decided what you could see.

Exercise 1 — Where would you look?

You want to know whether your own city is segregated.

What is the smallest unit you could get data for, and why does that choice change your answer?

Then: name one thing your measure would still miss entirely.

Five minutes, in pairs.

Exercise 1 — Responses

  • Mexico publishes four levels: estado → municipio → AGEB → manzana, the city block
  • The smaller the unit, the more segregation you find — big units average it away
  • A municipio of a million people can look mixed while every street in it is not

What your measure still misses: where people spend the day. Living apart and meeting are different things — people work, study and shop across the line.

Same city, two answers

Figure 11

Same 400 people. Same city. Drawn one way it is perfectly mixed; drawn another way it is completely divided. Nothing moved.

So what?

  • Sorting is measurable, and the measure depends on the unit
  • Prosperous-looking cities contain enormous internal gaps
  • Nothing so far tells us why the sorting happens

The obvious answer is that people are prejudiced. The obvious answer turns out to be unnecessary.

Schelling’s question

In 1971 Thomas Schelling asked what would happen if people were only mildly concerned about their neighbours.

Not hostile. Not seeking to exclude anyone. Simply preferring not to be an extreme minority on their own street.

He expected mild preferences to produce mild sorting.

What actually happens

Figure 12

Two lessons, pulling opposite ways

At the start, the average person’s neighbours were 50% their own group. At the end: 75%.

  • You do not need bigots to produce a segregated city
  • So finding segregation does not prove anyone is prejudiced
  • But it also does not prove that nobody is

The mechanism

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flowchart LR
  A["A mild<br/>preference"] --> B["A few<br/>people move"]
  B --> C["The street<br/>tips"]
  C --> D["Neighbours<br/>move too"]
  D -->|"and again"| B
  C --> E["Segregation"]
Figure 13

Author’s illustration, after Schelling (1971). The loop is the whole point.

Watch the street tip

An animated grid of red and green squares that starts mixed at random and separates into blocks of one colour over thirteen rounds.

Author’s simulation, after Schelling (1971). Each round, people with fewer than 30% same-colour neighbours swap houses with each other. Nobody’s preference changes.

But is anyone discriminating?

Schelling shows you do not need discrimination to divide a city. That is not evidence that there is none. So test it directly:

  • Send two applications for the same job
  • Make them identical except one detail: a name, a photo
  • Count who gets called back

Because everything else is held fixed, a gap in callbacks is hard to explain away.

What those tests find

Six passport-style photographs of applicants in business dress, arranged as women and men across three phenotypes labelled European, Mestiza or Mestizo, and Indigenous.

Same clothes. Same pose. Identical CV behind each one.

  • Arceo-Gómez and Campos-Vázquez sent these across Mexico
  • Indigenous-looking women were called back less
  • Men showed no penalty

Photographs: Arceo-Gómez & Campos-Vázquez, Appendix A. Bertrand and Mullainathan (2004) found a comparable gap in the United States using names alone.

Exercise 2 — Nothing explains it

A neighbourhood is 95% one group. You run all three tests:

Rents identical flats cost the same in both neighbourhoods
Landlords reply just as often to either name
Residents say they would be happy to live anywhere

Every explanation we have covered comes back clean.

Name two things that could still be producing it.

Five minutes, in pairs.

Exercise 2 — Responses

  • History. Who was allowed to buy where decades ago — and who inherited the house
  • Networks. You hear about the empty flat from people who live where you already live
  • The past, not the present. Mild preferences tipped the street once; nobody needs to hold them now
  • Measurement. What people say about neighbours is exactly what they under-report

Sorting can outlive every cause you can still measure. That is why repealing a law is not the same as undoing what it did.

Does living closer help?

Two intuitions, pointing opposite ways:

  • Contact breeds friction — difference itself is a source of conflict
  • Contact breeds familiarity — people who meet stop generalising

Huntington (1996) is the large-scale version of the first, written about civilizations rather than neighbourhoods. Allport (1954) made the second precise — and attached conditions to it.

Allport’s conditions

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flowchart LR
  A["Equal<br/>standing"] --> E["Less<br/>prejudice"]
  B["A shared<br/>goal"] --> E
  C["Working<br/>together"] --> E
  D["Institutional<br/>support"] --> E
Figure 14

Author’s illustration, after Allport (1954). Contact alone is not on the list.

The evidence, fifty years later

Pettigrew and Tropp (2006) pooled 515 studies. Contact reduces prejudice on average, and more reliably when Allport’s conditions hold.

  • Contact usually helps
  • Contact under the right conditions helps considerably more
  • Contact between unequals, competing, can make things worse

So what?

  • Contact requires proximity
  • Proximity is what segregation removes
  • A segregated city cannot run the experiment

Huntington asked whether different peoples can live together. The prior question is whether they are ever placed close enough to try.

Takeaways

  1. Mexico is diverse; most Mexican places are not
  2. Where a group lives is bound up with how it lives
  3. Sorting is measurable — and the number depends on the unit you pick
  4. Mild preferences can divide a city; discrimination is a separate, testable claim
  5. Contact reduces prejudice under conditions — the ones a divided city removes

The question is not whether people can live with difference. It is whether they are ever placed near enough to find out.

References

Allport, G. W. (1954). The Nature of Prejudice. Addison-Wesley.

Arceo-Gómez, E. O., & Campos-Vázquez, R. M. (2014). Race and marriage in the labor market: A discrimination correspondence study in a developing country. American Economic Review, 104(5), 376–380.

Bertrand, M., & Mullainathan, S. (2004). Are Emily and Greg more employable than Lakisha and Jamal? A field experiment on labor market discrimination. American Economic Review, 94(4), 991–1013.

CONEVAL. (2021). Medición de la pobreza a nivel municipio 2020. Mexico City: Consejo Nacional de Evaluación de la Política de Desarrollo Social.

Huntington, S. P. (1996). The Clash of Civilizations and the Remaking of World Order. Simon & Schuster.

References (cont.)

INEGI. (2021). Censo de Población y Vivienda 2020. Aguascalientes: Instituto Nacional de Estadística y Geografía.

Massey, D. S., & Denton, N. A. (1988). The dimensions of residential segregation. Social Forces, 67(2), 281–315.

Pettigrew, T. F., & Tropp, L. R. (2006). A meta-analytic test of intergroup contact theory. Journal of Personality and Social Psychology, 90(5), 751–783.

Schelling, T. C. (1971). Dynamic models of segregation. Journal of Mathematical Sociology, 1(2), 143–186.