Kerli’s Lectio Praecursoria

Capturing segregation through space and time: New insights from the activity space approach and big data

Lectio Praecursoria in the public examination of Kerli Müürisepp’s doctoral dissertation on 25 November 2023

Photo by Christoph Fink

The city of the twenty-first century is a site of diversity, connection, and opportunity.

Cities have never been as diverse as today in ethnic, socio-economic and demographic terms, nor with regard to attitudes, lifestyles and activities.

Much of that diversity is the outcome of the increasing mobility and migration of people, both within and across countries. The United Nations has estimated that over 280 million people live outside of their home country – this is more than half of the population of the European Union.

In Finland, the share of foreign-background people is still rather modest compared to its neighbours – Estonia and Sweden – and compared to many other European countries. Yet, roughly half of Finland’s foreign population live in the Helsinki region and the share is in rise. Undoubtedly, the Helsinki Metropolitan Area, has become a site of diversity.

Often, people move to cities with the hope for attaining better education, advancing in their career, and improving their quality of life. And they rightly do so – social diversity creates the values and the benefits of the contemporary city. By bringing different groups together and fostering connections between them, the socially diverse city ought to reduce prejudice and foster social cohesion; promote creativity, innovation, and economic performance. The socially diverse city ought to ensure social mobility – that is, provide equal opportunities to advance in life for all of us, regardless of our backgrounds.

What an ideal city it is.

But, the reality is far more complicated – the city is far from being ideal, is far from providing equal opportunities for all.

The city of the twenty-first century is also a site of difference, inequalities and segregation.

Diversity does not spread out evenly within cities. Inequalities that we have in the society tend to have a spatial footprint. Many cities are divided between the rich and the poor, and between the majority and the minority.

One of the most apparent expressions of such divisions – spatial segregation – is at the heart of my thesis. By spatial segregation, I mean the degree to which social groups live separately from one another.

I believe you have all heard about residential segregation, and seen photos of the ghettos of the disadvantaged next to gated communities of the advantaged. This is an example of extreme residential segregation. Unfortunately, it is not an exception, but an irrefutable reality in many cities around the world. And especially in cities, where there are large gaps between the rich and the poor.

In the European cities, and especially in the Nordics, we are lucky not to have such extreme levels of segregation. The Nordic welfare state social and urban policies are centred around the egalitarian idea of combating social inequalities, and providing equal opportunities to advance in life for all. At least to some extent, these policies have been successful. In the Helsinki Metropolitan Area, for example, residential segregation has stayed at the modest level by international standards. Still, we all live in socially different neighbourhoods, and probably have noticed that it is more common to hear English in the city centre, and Somali and Arabic in the Eastern parts of Helsinki. Social diversity varies from one neighbourhood to another.

At the same time, segregation is very much at the heart of public discussions in Finland. No week passes, without a newspaper article about segregation in Finnish cities, about socio-economic inequalities, about immigration and integration. Some of us, who come from a country with much higher inequalities and segregation, might even ask: are Finnish people overreacting? Why to worry about inequalities – Finland has the sixth lowest income inequality among OECD countries? Why to worry about residential segregation if it is modest by international standards? Why to worry if Finnish people have been named as the happiest in the world? For six years in a row?

Research shows – high levels of segregation can be harmful for both individuals, and in the long run, for societies more generally.

Let’s start with individuals. Many of us can’t afford to live where they want, but need to live where are the lowest rents, or where the social housing is located. In worst cases people end up tied to disadvantaged neighbourhoods. Research shows that this might have detrimental effects on their well-being and opportunities in life. And this is not only the problem of this individual who lives in the disadvantaged neighbourhood.

At societal level, segregation makes contacts between people with different backgrounds less likely, feeds into to the creation of stereotypes and prejudice, fractures social bonds, and threatens social cohesion in the society. And eventually such societal developments would influence us all.

This means, Finnish people are right to take segregation seriously. Segregation undermines the core principles of the Nordic Welfare model, undermines the core values of the Finnish society – to ensure equal opportunities to advance in life for everyone.

If cities are to perform their role as providing equal opportunities for all, cities need to take segregation at the heart of their policy agendas.

The City of Helsinki has taken this message more seriously than many others. Already, from 1970s, the city has followed social mixing principle in their housing policy to prevent the accumulation of disadvantage. During the current council term, one of the priority areas of the City Strategy is to “cultivate safe neighbourhoods with distinctive identities” with the goal “residential areas do not become segregated”. This is an excellent goal to have!

But, we are missing something important in this picture.

Segregation is not just a matter where you live, it’s the matter of places you actually visit and travel through.

Much of the segregation research and policy-making focusses on residential neighbourhoods. But our lives are not confined to residential neighbourhoods.

Let’s imagine, we are all neighbours. Although we start and end our days in the same neighbourhood, our daily lives are probably quite different. These take us to and through different places where we meet various people. Some of us might work in the city centre, some in the western campus of the university, some work mainly from home. For going to work, we might take a bus or a tram, we might walk or cycle, or drive a car. The various places we visit and travel through, and the activities we undertake, influence our experience of the city, and our interactions with the diverse people who surround us. Even though we might live in the same neighbourhood, our segregation experiences can be quite different.

Yet, people’s use of urban space beyond their residential neighbourhoods is seldom considered in segregation research and policymaking. But it should be considered. My thesis takes up this challenge, and calls for broadening the scope of segregation research. In other words. In my thesis, I argue for the importance of understanding segregation based on people’s actual activity locations and mobility.

Residential neighbourhoods are not the ones that produce segregation, people are the ones who produce segregation. Therefore, for a more comprehensive understanding of segregation, we need to capture the spatial divisions between social groups as their lives actually unfold daily, weekly, monthly, and yearly.

But don’t get me wrong. I’m not saying that segregation scholars, and policy-makers, have been ignorant about people’s actual everyday lives. The focus on residential segregation has been driven mainly by data availability. The main data sources that have been available for segregation research have been registry and census data. And these data sources seldom include spatial information other than where people live.

However, over the last two decades, we have seen several advances in social sciences that hold promise for moving towards a more comprehensive understanding of segregation. My thesis builds upon two of them, as you might see from its title. Namely, on 1) the activity space approach, and 2) spatial big data.

First, about the activity space approach. In segregation research, the activity space approach argues that spatial divisions between social groups are produced across all our activity locations, such as home, work, and shopping centre, and across the routes and areas we travel through.

Within my thesis, I made a literature review on the studies that have examined segregation across people’s various activity locations and mobility. This is referred to as Article I. The review shows: the activity space approach enables segregation to be studied from different perspectives – from the perspectives of people, places and mobility flows.

Second, my thesis pays particular attention to the use of spatial big data sources in segregation research. By spatial big data, I mean the high volumes of digital data that are constantly generated by our use of location-aware technologies, mobile devices and social media, to name a few. For instance, we all have a mobile phone in our bag or pocket. Each time we call, send a message, check our social media account, or just browse the internet, leaves a digital footprint in mobile phone operator’s database. These digital footprints that include spatial and temporal information allow researchers to study where and when people actually are.

In my thesis, I was interested to see how much different big data sources are used in segregation research, and what are their main benefits and limitations. My literature review, that I already mentioned, concluded: despite the limitations, mobile phone data are one of the most suitable data sources for capturing dynamic population-level segregation patterns.

Besides the literature review, my thesis comprises three empirical studies. All three studies build on the strengths of the activity space approach and use mobile phone data to provide new understanding on how segregation varies across space and time. Each empirical study focusses on a different capital city in the Nordic and Baltic Region: Article II on Tallinn in Estonia, Article III on Helsinki in Finland, and Article IV on Stockholm in Sweden.

Article II examines the differences in Estonian- and Russian-speakers’ activity spaces in Estonia over a day, over a month, and over a year. The study demonstrates: compared to Estonian-speakers, the minority group of Russian-speakers has much smaller activity spaces, and they tend to visit places where other Russian-speakers live. The differences are especially significant over annual activity spaces.

Article III examines people’s hour-by-hour use of urban space in the Helsinki Metropolitan Area. While my second article captured individuals’ activity spaces, Article III focusses on different types of residential communities. The study shows that the residents of disadvantaged neighbourhoods have a more isolated use of urban space than the residents of advantaged and mixed neighbourhoods.

Finally, Article IV takes a look at how abrupt societal disruptions influence segregation. In particular, it examines how the daytime social diversity varied week-by-week over the first wave of the COVID-19 pandemic in Greater Stockholm. My findings show that daytime social diversity decreased, meaning that people from different types of neighbourhoods had less opportunities to meet in the city, and that some groups became more isolated than others.

Overall, the results of my empirical studies demonstrate that people are segregated across their activity spaces, not just at home. My thesis further argues that segregation should be understood as a dynamic phenomenon that changes according to the mobility of people in the city and beyond. In specific, my findings indicate that people are more segregated beyond their daily routine activity spaces – during weekends and when they have holidays. And finally, my findings show that minorities and socio-economically disadvantaged groups are more isolated both residentially and across activity spaces than those in more advantaged positions.

The findings of my thesis highlight the need for a more integrated approach to urban social mixing policies – if the aim is to ensure social interaction and equal opportunities, we should look beyond residential policies. We should adopt indicators and measures that address the everyday mobility of people, and foster effective social mixing within the everyday urban life.

Remember, in the beginning I argued, that the city of the twenty-first century is a site of diversity, connection and opportunity. I believe everyone here would like to live in a city that provides equal opportunities for all. Segregation threatens us to live that dream – to live in a city for all.

But let’s not give up on this dream. Various advances in social sciences provide us new opportunities to move towards a more in-depth and integrated understanding of segregation. And ultimately, use this understanding in policy and planning to prevent and mitigate segregation.

I understand, this is not an easy task, and much remains to be explored. My thesis is one step forward in this quickly evolving research field of activity space segregation. One step forward to live in a city that provides equal opportunities for all.


Kerli Müürisepp defended her doctoral thesis entitled Capturing segregation through space and time: New insights from the activity space approach and big data” on 25 November 2023 at the Faculty of Science, University of Helsinki.

Professor Mei-Po Kwan from The Chinese University of Hong Kong acted as the opponent and Professor Tuuli Toivonen as the custos. Kerli was supervised by Docent, senior researcher Olle Järv, Professor Tuuli Toivonen, and Professor Tiit Tammaru.

Kerli completed her doctoral thesis in the Digital Geography Lab research group under the project “Socio-spatial dialogues in the city: Tracing spatial mobilities, social engagement and integration using big data”, funded by the Kone Foundation. In addition, Kerli’s work has beed supported by the City of Helsinki Research Grant, the Academy of Finland-funded BORDERSPACE project, and the YLLI-project (funded from the development and research programme “Lähiöohjelma 2020–2022”).

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