Piotr Denderski is an economist, a member of the Institute of Economics at the Polish Academy of Sciences, and an Associate Professor at the University of Leicester. He is currently spending three months as a Fernand Braudel Senior Fellow at the EUI Department of Economics. His fellowship is funded through the EUI Widening Europe Programme, which, in his words, “provides a strong platform to broaden professional networks, receive feedback on current research, and spark long-term international research collaborations—all within the inspiring surroundings of Florence and Fiesole.”
In this interview, Denderski shares insights into the research projects he is working on during his fellowship, which examine how marital and relationship status shape key labour market decisions.
Why do economists focus on marriage in the first place? What role do relationships play in an economy?
We all start life as singles, but a lot of us eventually form partnerships or start families. While we naturally think of relationships in romantic terms, economists view relationships and families as key private insurance mechanisms against adversities.
If you are single and face a setback—such as a layoff or an illness—you have to navigate that shock alone. In a couple or family, however, a partner's income and care provide a crucial cushion against a health crisis or an unexpected job loss.
The first project you are working on evaluates how tax designs and unemployment benefits affect couples. Could you explain this research and its main findings so far?
Economic policies, particularly tax and benefit systems, often treat individuals differently depending on their marital status. In countries such as the US and my home country, Poland, married couples can choose to file their tax returns individually or jointly. Joint filing allows couples to combine their incomes. While this can lower a household's overall tax bill—especially when one partner earns significantly more than the other—it comes with a major drawback: It can discourage lower-earning spouses from entering the workforce or seeking higher-paying jobs, as their additional income would be taxed at a higher rate.
To study these dynamics, I built a mathematical model that mimics real-world decisions—how couples navigate job loss, save for unexpected expenses, and decide which job offers to accept or reject. I then used this model as a laboratory to test different policy reforms. When economists evaluate whether to reform existing policies or introduce new ones, our primary role is to first establish a benchmark: determining how far current practice is from the best achievable outcome.
My findings suggest that current US policy, for instance, is fundamentally flawed. First, tax systems ought to lean toward taxing individuals rather than joint households to encourage lower-earning spouses to work without facing tax penalties. Second, unemployment benefits should account for the broader household context rather than focusing strictly on individual past earnings. In the US, unemployment benefits depend almost entirely on a worker's prior income—typically covering roughly 40% of previous wages for a few months—regardless of whether their partner is employed.
However, the model shows that past wages should matter less, while household employment status should matter much more. Unemployment benefits could be significantly lower—around 8 to 10%—if one partner remains employed, but higher—from 40 to 50%—when both partners are out of work, given that dual-unemployed households face far more severe financial distress.
This project focuses on the US due to its detailed data and its economic size. However, the core insights extend to Europe as well. Many European countries use progressive tax rates and offer longer unemployment benefits—the latter of which runs the risk, in my view, of over-subsidising out-of-work periods.
In a second project, you explore ideal employment contracts versus real-world market constraints. What would an ideal job contract look like and why don't companies offer contracts like that?
In an ideal world, employment contracts would be flexible and adapt to a worker's personal life. For instance, a firm could temporarily raise an employee’s wage if their spouse loses a job and then lower it back down once the spouse finds employment.
However, real-world constraints prevent this from happening. Economists call this the "private information problem." Because employers cannot easily verify a spouse's true employment status, workers would have a financial incentive to lie to their employers—for instance, by delaying reporting when their partner finds work to keep receiving higher pay. On top of this risk of dishonesty, constantly renegotiating contracts whenever a spouse's job situation changes would be extremely costly and impractical for businesses.
Because private labour markets face these structural information barriers, ideal contracts remain out of reach. This is precisely why governments must step in with well-designed tax and benefit systems to fill the gap—though policymakers must be careful not to over-insure workers and inadvertently discourage them from seeking employment.
How do factors like children or single-person households fit into your broader research on contracts, taxes, and financial vulnerability?
In the projects we are discussing, I set aside the role of children to keep the mathematical model manageable and maintain a clear focus on the core tax and benefit mechanisms I was testing. That said, children clearly make a significant economic difference in a family's finances, and I have begun exploring this dynamic in another project. For example, childbirth often widens the gender pay gap, as it is frequently the point at which some women reduce their working hours, do not try hard to be promoted, or leave the workforce entirely.
As for singles, contract negotiations are simpler because only two parties are involved—the employer and the employee—whereas with couples, an ideal contract would account for the broader household situation. However, singles are undoubtedly in a more vulnerable position during layoffs because they lack a partner to provide a financial cushion. Addressing their needs opens a distinct line of inquiry. While my fellowship work focuses primarily on couples, another branch of my research compares consumption patterns between singles and couples to help determine how tax burdens should differ between them. Ultimately, the financial realities of single- and dual-person households are starkly different, and public policy must account for both.
Piotr Denderski is a Fernand Braudel Senior Fellow at the EUI Department of Economics from 1 September to 30 November 2026. Denderski is a member of the Institute of Economics at the Polish Academy of Sciences and an Associate Professor at the School of Economics of the University of Leicester. His main research interests are macroeconomics and labour economics. He collaborates on the projects discussed in this interview with Economics Professor Leo Kaas, his host at the EUI Economics Department, and with academics from institutions in Austria (Dr Nawid Siassi, Technische Universität Wien) and Denmark (Dr Bastian Schulz, Aarhus University).
The Fernand Braudel Fellowship special call for applications was launched in the framework of the EUI Widening Europe Programme, which is supported by contributions from the European Union and EUI Contracting States. The programme is designed to strengthen internationalisation, competitiveness, and quality in research in targeted Widening countries.