Tag Archives | Analytical Sociology

Bending the Heckman Curve: Competing Declines in Learning Capacity and Skill Relevance Over the Life Course

João M. Souto-Maior, Mitchell L. Stevens

Sociological Science August 4, 2026
10.15195/v13.a35


The Heckman curve has powerfully influenced social policy by providing mathematical support for the concentration of human-capital investments early in the life course. The canonical model behind this curve derives a single relationship for aggregate human capital and does not address how return trajectories vary across skill types. We extend the canonical mathematical framework to derive skill-specific return trajectories, incorporating two key parameters governing declines in (a) human capacity to learn and (b) skill relevance over the life course. Our microfoundation model implies that the shape of return trajectories depends on the relative magnitudes of these two declines, indicating a trade-off: although early investments may be more efficient due to declining human learning capacity, they risk misalignment with future labor market needs. Depending on the targeted skill, investments in adult workers might more effectively align with evolving skill content. We illustrate this result with numerical simulations using empirically plausible parameter ranges and selected skill profiles. Our work suggests that optimal investment timing may be skill-dependent, and identifies empirical questions that can better inform human-capital policy in a time of rapid technological change and lengthening lifespans.

Creative Commons LicenseThis work is licensed under a Creative Commons Attribution 4.0 International License.


João M. Souto-Maior: Stanford Center on Longevity and Graduate School of Education, Stanford University.
E-mail: joao.msoutomaior@gmail.com.

Mitchell L. Stevens: Graduate School of Education and Stanford Center on Longevity, Stanford University.
E-mail: stevens4@stanford.edu.

Acknowledgments: This paper is part of the project “Education and Learning for Longer Lives,” sponsored by the Stanford Center on Longevity (SCL) in 2025–2026. We thank the SCL’s Futures Fellows and New Map of Life Postdoctoral Fellows for the contexts in which this work germinated. We are especially grateful to Bernardo Mackenna, Chris Heitzig, Leon Marbach, and Arik Lifschitz for written feedback, and to Matt Sigelman for valuable advice. Earlier versions of this work benefited from critical feedback (all in 2025) in Stanford’s Pathways Network Seminar and Inequality Workshop, the SCL Fellows Seminar, the Sociological Science Annual Conference, and the International Network of Analytical Sociology Conference. Any errors are our own.


Supplemental Materials

Data and code availability statement: This paper does not use external data. Full replication code for numerical simulations and figures available at: https://github.com/joaosoutomaior/competing-declines-code.


  • Citation: Souto-Maior, João M., and Mitchell L. Stevens. 2026. “Bending the Heckman Curve: Competing Declines in Learning Capacity and Skill Relevance Over the Life Course” Sociological Science 13: 915-944.
  • Received: April 9, 2026
  • Accepted: June 16, 2026
  • Editors: Stephen Vaisey, Herman van de Werfhorst
  • DOI: 10.15195/v13.a35


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Why Your Friends Are More Important and Special Than You Think

Thomas U. Grund

Sociological Science, April 14, 2014
DOI 10.15195/v1.a10

A large amount of research finds associations between individuals’ attributes and the position of individuals in network structures. In this article, I illustrate how such associations systematically affect the assessment of attributes through network neighbors. The friendship paradox—a general regularity in network contexts, which states that your friends are likely to have more friends than you—becomes relevant and extends to individuals’ attributes as well. First, I show that your friends are likely to be better informed (closeness), better intermediaries (betweenness) and more powerful (eigenvector) than you. Second, I suggest more generally that your friends are likely to be more special in their attributes than the population at large. Finally, I investigate the implications of this phenomenon in a dynamic setting. Applying calibrated agent-based simulations, I use a model of attribute adoption to emphasize how structurally introduced experiences penetrate the trajectory of social processes. Existing research does not yet adequately acknowledge this phenomenon.

Thomas U. Grund: Stockholm University. E-mail: thomas.u.grund@gmail.com

  • Citation: Thomas U. Grund. 2014. “Why Your Friends Are More Important and Special Than You Think.” Sociological Science 1: 128–140
  • Received: December 14, 2013
  • Accepted: December 27, 2o13
  • Editors: Jesper Sørensen, Ezra Zuckerman
  • DOI: 10.15195/v1.a10

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