Simon's model does not produce Zipf's law: The fundamental rich-get-richer mechanism for any power-law size ranking

Fuente: arXiv
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Autores principales: Rosillo-Rodes, Pablo, Zimmerman, Julia Witte, Hébert-Dufresne, Laurent, Dodds, Peter Sheridan
Formato: Preprint
Publicado: 2026
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author Rosillo-Rodes, Pablo
Zimmerman, Julia Witte
Hébert-Dufresne, Laurent
Dodds, Peter Sheridan
author_facet Rosillo-Rodes, Pablo
Zimmerman, Julia Witte
Hébert-Dufresne, Laurent
Dodds, Peter Sheridan
contents Many complex systems are composed of disparate, interacting types of varying sizes: Species abundances in ecosystems, firm sizes in markets, city populations in countries, word counts in language, etc. A longstanding mystery of complex systems is Zipf's law, which is the empirical observation that component size decreases as the inverse of component rank -- $S \propto r^{-1}$ -- and its generalization $S \propto r^{-α}$ for $α\ge 0$. Herbert Simon's 1955 theoretical rich-get-richer mechanism for system growth has prevailed as capturing the essential process. But Simon's analysis is in fact flawed: In the limit of zero innovation, the model leads to a winner-takes-all system with $α\rightarrow \infty$, rather than $α\rightarrow 1$. Here, for pure rich-get-richer systems, we derive the time-dependent innovation rate $ρ_t$ that correctly produces power-law size rankings across all $α\ge 0$. To produce Zipf's law, we uncover that $ρ_t$ must decay as the inverse of the log of the number of types, $1/\ln N$. We then show that our time-dependent innovation rate governs type emergence in any system obeying a power-law size-ranking, independent of the underlying mechanism. We demonstrate agreement between our model's output and word rankings in a collection of famous novels, while Simon's model fails. Going forward, our dynamic innovation rate mechanism provides the fundamental, Drosophila-like model for all rich-get-richer systems.
format Preprint
id arxiv_https___arxiv_org_abs_2604_13184
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Simon's model does not produce Zipf's law: The fundamental rich-get-richer mechanism for any power-law size ranking
Rosillo-Rodes, Pablo
Zimmerman, Julia Witte
Hébert-Dufresne, Laurent
Dodds, Peter Sheridan
Physics and Society
Many complex systems are composed of disparate, interacting types of varying sizes: Species abundances in ecosystems, firm sizes in markets, city populations in countries, word counts in language, etc. A longstanding mystery of complex systems is Zipf's law, which is the empirical observation that component size decreases as the inverse of component rank -- $S \propto r^{-1}$ -- and its generalization $S \propto r^{-α}$ for $α\ge 0$. Herbert Simon's 1955 theoretical rich-get-richer mechanism for system growth has prevailed as capturing the essential process. But Simon's analysis is in fact flawed: In the limit of zero innovation, the model leads to a winner-takes-all system with $α\rightarrow \infty$, rather than $α\rightarrow 1$. Here, for pure rich-get-richer systems, we derive the time-dependent innovation rate $ρ_t$ that correctly produces power-law size rankings across all $α\ge 0$. To produce Zipf's law, we uncover that $ρ_t$ must decay as the inverse of the log of the number of types, $1/\ln N$. We then show that our time-dependent innovation rate governs type emergence in any system obeying a power-law size-ranking, independent of the underlying mechanism. We demonstrate agreement between our model's output and word rankings in a collection of famous novels, while Simon's model fails. Going forward, our dynamic innovation rate mechanism provides the fundamental, Drosophila-like model for all rich-get-richer systems.
title Simon's model does not produce Zipf's law: The fundamental rich-get-richer mechanism for any power-law size ranking
topic Physics and Society
url https://arxiv.org/abs/2604.13184