I began studying economics in 1992, straight after upper secondary school, hoping to learn about exchange rates and macroeconomics. This was when the European monetary cooperation that would later lead to the euro was taking shape. But after my second-year exams, my interests took a completely different turn.<\/p>\n
A work that changed everything<\/p>\n
What book, film, academic text or encounter with art can change a person\u2019s life?<\/p>\n
In this series, six researchers and university figures talk about the work that changed the way they think, conduct research or live.<\/p>\n
This is the first chapter.<\/p>\n<\/div>\n
It was spring 1994, in Anneks A and B \u2014 the lecture halls on Studiestr\u00e6de in central Copenhagen that will be familiar to many.<\/p>\n
Microeconomics was taught using the so-called green notes. Anyone who studied economics back then will remember the green notes. These were teaching notes written by the macroeconomics and microeconomics lecturers, and the microeconomics notes were \u2014 to be perfectly honest \u2014 heavy going.<\/p>\n
They were typewritten, the paper was rather coarse and, on a good day, there were no more than one or two sentences in plain Danish that actually explained why the questions mattered. On top of that, it was fiendishly difficult.<\/p>\n
One of the topics in the spring of 1994 was welfare economics: how we, as a society, assess whether and how different allocations of resources and different policy measures affect both individual and overall welfare.<\/p>\n
Yes, it\u2019s complicated. But decisions still have to be made. And what is overall, or aggregate, welfare? Does it exist, and can it be measured?<\/p>\n
It was here, in my second year, that I was introduced to Arrow\u2019s impossibility theorem.<\/p>\n
A theorem is mathematical jargon for a statement that has been proved and is particularly profound or important.<\/p>\n
BIOGRAPHY<\/p>\n
David Dreyer Lassen is Rector of the University of Copenhagen and Professor of Economics at the same institution.<\/p>\n
He holds a master\u2019s degree in economics (1998) and a PhD (2002), both from the University of Copenhagen.<\/p>\n
He chairs Videnskab.dk\u2019s advisory board, Innovation District Copenhagen and the science park Symbion A\/S, and is a member of the Royal Danish Academy of Sciences and Letters.<\/p>\n<\/div>\n
Many decisions are made by and affect groups \u2014 families, boards, organisations, Denmark as a whole. So when can we say that a collective decision, A or B, is best for the group?<\/p>\n
The answer is: generally, we cannot. Best wishes, Kenneth Arrow. He analysed the problem in his PhD thesis in the late 1940s and was awarded the Nobel Prize partly for this work.<\/p>\n
So what does the theorem mean? Consider a group that has to choose between at least three options.<\/p>\n
Arrow\u2019s theorem states \u2014 roughly speaking \u2014 that no voting system can turn individual group members\u2019 rankings of the three options into a single ranking for the group while also meeting four reasonable requirements: it must be able to accommodate every conceivable combination of preferences; if everyone prefers A to B, the group must do so too; the group\u2019s choice between A and B must not depend on what people think of a third option, C; and no single person may dictate the outcome.<\/p>\n
Arrow\u2019s work laid the foundations of modern social choice theory and turned welfare economics upside down<\/p><\/blockquote>\n
Each requirement can be met individually, but they cannot all be met at once.<\/p>\n
I was hooked<\/h3>\n
For me, the experience back then, after my second-year exams, had two dimensions: first, there was the substance of the theorem itself \u2014 no, economic analysis alone cannot actually tell us what Denmark should do \u2014 and second, and more importantly, the broader insight that rigour, logic and mathematical tools could be used to study democratic processes and how economic policy is made.<\/p>\n
Arrow\u2019s work laid the foundations of modern social choice theory and turned welfare economics upside down.<\/p>\n
I never went on to work specifically on social choice myself, but it sparked my interest in what is known as political economics: rather than studying the consequences of a given economic policy, political economics focuses on why one policy is chosen over another.<\/p>\n
I was hooked on the subject. I specialised in it during my master\u2019s degree, wrote my thesis on it and was awarded a PhD scholarship at a basic research centre where I had worked as a student assistant for several years.<\/p>\n
As part of my PhD, I spent a year at Harvard University, which was \u2014 and remains \u2014 particularly strong in this field.<\/p>\n
Two Nobel laureates and an email<\/h3>\n
Although I was not working directly on social choice myself, I could not resist taking a course on it when I had the opportunity at Harvard.<\/p>\n
The course was taught by Amartya Sen, another Nobel laureate, and in many ways it was an extraordinary experience: alongside around 30 students from various disciplines, there were many professors in attendance, as well as a couple of visiting professors (and their spouses!) of a similar calibre.<\/p>\n
It combined some of the most challenging material at one of the world\u2019s best universities with something best described as a public lecture series \u2014 albeit a highly selective one. All delivered by a man of the world who drew freely on examples in many languages and from across cultures.<\/p>\n
Several lectures focused specifically on the impossibility theorem and Sen\u2019s own subsequent work: the idea that the impossibility is partly of our own making.<\/p>\n
Arrow allows only information about what people prefer \u2014 not how strongly they prefer it. Allow for the latter, and for the fact that some people have more at stake than others, and the impossibility becomes less absolute.<\/p>\n
Debate was heated, and during the course Sen had to consult Arrow by email to clarify an interpretation. So there we were, watching two Nobel laureates correspond about what exactly one of them had proved half a century earlier.<\/p>\n
Since my PhD, I have worked across economics and political science. Arrow\u2019s impossibility theorem never became my own field of research, but encountering it on Studiestr\u00e6de in 1994 changed the question that interested me: not just what consequences economic policy has, but why we choose one policy over another.<\/p>\n
This article was translated with the assistance of artificial intelligence and subsequently reviewed by a member of the editorial staff.<\/em>
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work that changed everything","text":"This is a story about what will follow","use_post_excerpt":true},{"acf_fc_layout":"Byline","is_author":false,"contributors":[{"use_registered_user":false,"user":false,"contributor_name":"David Dreyer Lassen","contributor_title":"Rector of the University of Copenhagen and Professor of Economics","contributor_image":false}]},{"acf_fc_layout":"Content","content":"<p>I began studying economics in 1992, straight after upper secondary school, hoping to learn about exchange rates and macroeconomics. This was when the European monetary cooperation that would later lead to the euro was taking shape. But after my second-year exams, my interests took a completely different turn.<\/p>\n<div class=\"factbox\">\n<p class=\"factbox-header feature-color\">A work that changed everything<\/p>\n<p>What book, film, academic text or encounter with art can change a person\u2019s life?<\/p>\n<p>In this series, six researchers and university figures talk about the work that changed the way they think, conduct research or live.<\/p>\n<p>This is the first chapter.<\/p>\n<\/div>\n<p>It was spring 1994, in Anneks A and B \u2014 the lecture halls on Studiestr\u00e6de in central Copenhagen that will be familiar to many.<\/p>\n<p>Microeconomics was taught using the so-called green notes. Anyone who studied economics back then will remember the green notes. These were teaching notes written by the macroeconomics and microeconomics lecturers, and the microeconomics notes were \u2014 to be perfectly honest \u2014 heavy going.<\/p>\n<p>They were typewritten, the paper was rather coarse and, on a good day, there were no more than one or two sentences in plain Danish that actually explained why the questions mattered. On top of that, it was fiendishly difficult.<\/p>\n<p>One of the topics in the spring of 1994 was welfare economics: how we, as a society, assess whether and how different allocations of resources and different policy measures affect both individual and overall welfare.<\/p>\n<p>Yes, it\u2019s complicated. But decisions still have to be made. And what is overall, or aggregate, welfare? Does it exist, and can it be measured?<\/p>\n<h3>Best wishes, Kenneth Arrow<\/h3>\n<p>It was here, in my second year, that I was introduced to Arrow\u2019s impossibility theorem.<\/p>\n<p>A theorem is mathematical jargon for a statement that has been proved and is particularly profound or important.<\/p>\n<div class=\"factbox\">\n<p class=\"factbox-header feature-color\">BIOGRAPHY<\/p>\n<p>David Dreyer Lassen is Rector of the University of Copenhagen and Professor of Economics at the same institution.<\/p>\n<p>He holds a master\u2019s degree in economics (1998) and a PhD (2002), both from the University of Copenhagen.<\/p>\n<p>He chairs Videnskab.dk\u2019s advisory board, Innovation District Copenhagen and the science park Symbion A\/S, and is a member of the Royal Danish Academy of Sciences and Letters.<\/p>\n<\/div>\n<p>Many decisions are made by and affect groups \u2014 families, boards, organisations, Denmark as a whole. So when can we say that a collective decision, A or B, is best for the group?<\/p>\n<p>The answer is: generally, we cannot. Best wishes, Kenneth Arrow. He analysed the problem in his PhD thesis in the late 1940s and was awarded the Nobel Prize partly for this work.<\/p>\n<p>So what does the theorem mean? Consider a group that has to choose between at least three options.<\/p>\n<p>Arrow\u2019s theorem states \u2014 roughly speaking \u2014 that no voting system can turn individual group members\u2019 rankings of the three options into a single ranking for the group while also meeting four reasonable requirements: it must be able to accommodate every conceivable combination of preferences; if everyone prefers A to B, the group must do so too; the group\u2019s choice between A and B must not depend on what people think of a third option, C; and no single person may dictate the outcome.<\/p>\n<blockquote><p>Arrow\u2019s work laid the foundations of modern social choice theory and turned welfare economics upside down<\/p><\/blockquote>\n<p>Each requirement can be met individually, but they cannot all be met at once.<\/p>\n<h3>I was hooked<\/h3>\n<p>For me, the experience back then, after my second-year exams, had two dimensions: first, there was the substance of the theorem itself \u2014 no, economic analysis alone cannot actually tell us what Denmark should do \u2014 and second, and more importantly, the broader insight that rigour, logic and mathematical tools could be used to study democratic processes and how economic policy is made.<\/p>\n<p>Arrow\u2019s work laid the foundations of modern social choice theory and turned welfare economics upside down.<\/p>\n<p>I never went on to work specifically on social choice myself, but it sparked my interest in what is known as political economics: rather than studying the consequences of a given economic policy, political economics focuses on why one policy is chosen over another.<\/p>\n<p>I was hooked on the subject. I specialised in it during my master\u2019s degree, wrote my thesis on it and was awarded a PhD scholarship at a basic research centre where I had worked as a student assistant for several years.<\/p>\n<p>As part of my PhD, I spent a year at Harvard University, which was \u2014 and remains \u2014 particularly strong in this field.<\/p>\n<h3>Two Nobel laureates and an email<\/h3>\n<p>Although I was not working directly on social choice myself, I could not resist taking a course on it when I had the opportunity at Harvard.<\/p>\n<p>The course was taught by Amartya Sen, another Nobel laureate, and in many ways it was an extraordinary experience: alongside around 30 students from various disciplines, there were many professors in attendance, as well as a couple of visiting professors (and their spouses!) of a similar calibre.<\/p>\n<p>It combined some of the most challenging material at one of the world\u2019s best universities with something best described as a public lecture series \u2014 albeit a highly selective one. All delivered by a man of the world who drew freely on examples in many languages and from across cultures.<\/p>\n<p>Several lectures focused specifically on the impossibility theorem and Sen\u2019s own subsequent work: the idea that the impossibility is partly of our own making.<\/p>\n<p>Arrow allows only information about what people prefer \u2014 not how strongly they prefer it. Allow for the latter, and for the fact that some people have more at stake than others, and the impossibility becomes less absolute.<\/p>\n<p>Debate was heated, and during the course Sen had to consult Arrow by email to clarify an interpretation. So there we were, watching two Nobel laureates correspond about what exactly one of them had proved half a century earlier.<\/p>\n<p>Since my PhD, I have worked across economics and political science. Arrow\u2019s impossibility theorem never became my own field of research, but encountering it on Studiestr\u00e6de in 1994 changed the question that interested me: not just what consequences economic policy has, but why we choose one policy over another.<\/p>\n<p><em>This article was translated with the assistance of artificial intelligence and subsequently reviewed by a member of the editorial staff.<\/em><\/p>\n"},{"acf_fc_layout":"ArticleEnd"},{"acf_fc_layout":"Newsletter","lang_select":"da","identifier":"Nyhedsbrev","headline":"Modtag et ugentligt nyhedsoverblik i din inbox","button_text":"Tilmeld nu","class":""},{"acf_fc_layout":"OtherStories","headline":"","hand_picked_posts":false,"references":false,"category":false,"theme":false,"number_of_posts":"4","style":"default"}]},"taxonomyData":{"category":[{"term_id":8907,"name":"Kronik","slug":"kronik","term_group":0,"term_taxonomy_id":8907,"taxonomy":"category","description":"","parent":0,"count":1,"filter":"raw"},{"term_id":47,"name":"Opinion","slug":"opinion","term_group":0,"term_taxonomy_id":47,"taxonomy":"category","description":"","parent":0,"count":336,"filter":"raw"}],"post_tag":[{"term_id":2254,"name":"David Dreyer Lassen","slug":"david-dreyer-lassen-en","term_group":0,"term_taxonomy_id":2254,"taxonomy":"post_tag","description":"","parent":0,"count":8,"filter":"raw"},{"term_id":8908,"name":"Et v\u00e6rk der \u00e6ndrede alt","slug":"et-vaerk-der-aendrede-alt","term_group":0,"term_taxonomy_id":8908,"taxonomy":"post_tag","description":"","parent":0,"count":1,"filter":"raw"},{"term_id":8909,"name":"\u00f8konomistudiet","slug":"oekonomistudiet","term_group":0,"term_taxonomy_id":8909,"taxonomy":"post_tag","description":"","parent":0,"count":1,"filter":"raw"}],"post_format":[],"expression":[{"term_id":16,"name":"Opinion","slug":"opinion","term_group":0,"term_taxonomy_id":16,"taxonomy":"expression","description":"","parent":0,"count":2093,"filter":"raw"}],"translation_priority":[{"term_id":5468,"name":"Optional","slug":"optional-en","term_group":0,"term_taxonomy_id":5468,"taxonomy":"translation_priority","description":"","parent":0,"count":694,"filter":"raw"}]},"featured_media_url":"https:\/\/uniavisen.dk\/wp-content\/uploads\/2026\/09\/david_dreyer_lassen_y9a6285-1280x854.jpg","_links":{"self":[{"href":"https:\/\/uniavisen.dk\/en\/wp-json\/wp\/v2\/posts\/193383","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/uniavisen.dk\/en\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/uniavisen.dk\/en\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/uniavisen.dk\/en\/wp-json\/wp\/v2\/users\/109"}],"replies":[{"embeddable":true,"href":"https:\/\/uniavisen.dk\/en\/wp-json\/wp\/v2\/comments?post=193383"}],"version-history":[{"count":6,"href":"https:\/\/uniavisen.dk\/en\/wp-json\/wp\/v2\/posts\/193383\/revisions"}],"predecessor-version":[{"id":193389,"href":"https:\/\/uniavisen.dk\/en\/wp-json\/wp\/v2\/posts\/193383\/revisions\/193389"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/uniavisen.dk\/en\/wp-json\/wp\/v2\/media\/193152"}],"wp:attachment":[{"href":"https:\/\/uniavisen.dk\/en\/wp-json\/wp\/v2\/media?parent=193383"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/uniavisen.dk\/en\/wp-json\/wp\/v2\/categories?post=193383"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/uniavisen.dk\/en\/wp-json\/wp\/v2\/tags?post=193383"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}