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arxiv: 2507.09419 · v5 · submitted 2025-07-12 · 💰 econ.GN · q-fin.EC

Peer Influence on West Point Cadets' Civil War Allegiances

Yuchen Guo , Matthew O. Jackson , Ruixue Jia This is my paper

Pith reviewed 2026-05-19 04:11 UTC · model grok-4.3

classification 💰 econ.GN q-fin.EC
keywords peer influenceCivil WarWest Point cadetsallegiance choicesocial networksUnion Armyslave statesfree states
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The pith

West Point cadets from slave states were more likely to join the Union Army when they had more free-state classmates.

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The paper examines whether peer influence shaped major decisions during the deep divisions of the American Civil War. It focuses on how West Point cadets chose which army to join. Using shifts in the share of classmates from free states across different classes, the authors show that greater exposure to free-state peers raised the chance that cadets from slave states fought for the Union. The strength of this influence depended on where the cadet came from and whether he owned slaves, and it increased when cadets had fought together before or served in the same group. The results point to social circles inside a single institution as a force that can change allegiances even in national conflict.

Core claim

A higher proportion of classmates from Free States significantly increased the likelihood that cadets from Slave States joined the Union Army. The peer effect varied with geography, appearing stronger in home states or counties with lower slave population shares and among cadets who themselves owned slaves in 1860. Peer effects grew larger with sustained interaction, including prior service together in the Mexican-American War, continuous military service, and membership in the same cohort.

What carries the argument

Quasi-random variation in the proportion of cadets from Free States across West Point classes, which identifies the causal effect of peer composition on the choice between Union and Confederate service.

Load-bearing premise

The share of free-state cadets in each class changes for reasons unrelated to any other traits that would directly affect a slave-state cadet's decision about which army to join.

What would settle it

A finding that classes with more free-state cadets also differed systematically in the family backgrounds, pre-war views, or home-county characteristics of the slave-state cadets placed in them.

Figures

Figures reproduced from arXiv: 2507.09419 by Matthew O. Jackson, Ruixue Jia, Yuchen Guo.

Figure 1
Figure 1. Figure 1: Home-state slave share and the probability of joining the Union Note. This figure plots the relationship between the share of the slave population in a state and the likelihood that cadets from that state would join the Union. Panel A concentrates on the states that participated in the war, while Panel B uses all cadets, including those who did not participate in the war. The circle’s size represents the n… view at source ↗
Figure 2
Figure 2. Figure 2: Relevance of Peers: Motivating Evidence (a) Free-State peers and allegiances for two groups of cadets (b) Peer composition over time Note. Panel (a) shows the relationship between the share of Free-State peers and the probability of joining the Union, depicted separately for war-participating cadets from Free and Slave States. Peer influence appears stronger among the latter. Panel (b) presents the time-se… view at source ↗
read the original abstract

Do social networks and peer influence shape major life decisions in highly polarized settings? We explore this question by examining how peers influenced the allegiances of West Point cadets during the American Civil War. Leveraging quasi-random variations in the proportion of cadets from Free States, we analyze how cadets' decisions about which army to join depended on the composition of their peers. We have three main findings. First, there was a strong and significant peer effect: a higher proportion of classmates from Free States significantly increased the likelihood that cadets from Slave States joined the Union Army. Second, the peer effect varies with geography, most notably with the slave population share in cadets' home states or counties, and with cadets' own slave ownership in 1860. Third, peer effects were amplified by shared experiences such as having served together in the Mexican-American War, continuous military service, and belonging to the same cohort, suggesting that sustained interaction is important.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit. Tearing a paper down is the easy half of reading it; the pith above is the substance, this is the friction.

Referee Report

2 major / 2 minor

Summary. The paper examines whether peer influence shaped West Point cadets' decisions to join the Union or Confederate armies during the American Civil War. It exploits quasi-random variation in the share of classmates from Free States within graduating classes to estimate peer effects, focusing on cadets from Slave States. The main findings are a statistically significant positive peer effect on joining the Union Army, heterogeneity by home-state or county slave population share and by the cadet's own 1860 slave ownership, and amplification of the effect when cadets shared prior service in the Mexican-American War, continuous military careers, or the same cohort.

Significance. If the identification strategy is valid, the paper offers valuable historical evidence on how social networks affect high-stakes allegiance choices in polarized environments. The heterogeneity results and emphasis on sustained interaction provide additional texture that could inform theories of peer effects. The setting is distinctive, but the contribution hinges on demonstrating that class composition is plausibly exogenous to the unobservables driving allegiance.

major comments (2)
  1. [Empirical Strategy] Empirical Strategy section: the claim that within-class variation in the Free-State classmate share is quasi-random is asserted but not supported by balance tables on observables, pre-trend checks, or a description of West Point admission rules and volumes. This assumption is load-bearing for the headline result; any correlation between admission patterns and sectional political tensions or home-state traits would bias the estimated peer effect on Union allegiance for Slave-State cadets.
  2. [Results] Main results (likely Table 2 or the regression reported in §4): the abstract states statistical significance and heterogeneity but the manuscript must report the exact sample size, the functional form of the peer-share variable, standard errors, and at least one robustness check (e.g., cohort fixed effects or alternative clustering) to allow evaluation of the magnitude and stability of the coefficient on Free-State share.
minor comments (2)
  1. [Abstract] Abstract: include a sentence on sample size and a one-sentence summary of the identification approach so that the strength of the claims can be assessed from the abstract alone.
  2. [Notation] Notation: define the peer-share variable and the outcome (Union vs. Confederate service) explicitly in the first results table or equation for clarity.

Simulated Author's Rebuttal

2 responses · 0 unresolved

We are grateful to the referee for their detailed and insightful comments, which have helped us improve the manuscript. We address each of the major comments below and indicate the revisions made.

read point-by-point responses

  1. Referee: [Empirical Strategy] Empirical Strategy section: the claim that within-class variation in the Free-State classmate share is quasi-random is asserted but not supported by balance tables on observables, pre-trend checks, or a description of West Point admission rules and volumes. This assumption is load-bearing for the headline result; any correlation between admission patterns and sectional political tensions or home-state traits would bias the estimated peer effect on Union allegiance for Slave-State cadets.

    Authors: We acknowledge the importance of substantiating the quasi-random assignment of classmates. In the revised manuscript, we have included balance tests on key observables such as home state characteristics, prior military experience, and family background to show that the share of Free State classmates is uncorrelated with these factors. We have also added a detailed description of West Point's admission process during the period, noting that class assignments were largely based on congressional district nominations with limited scope for self-selection based on sectional tensions. While pre-trend checks are limited by the historical nature of the data, we argue that the timing of the Civil War and the structure of admissions make systematic bias unlikely. These additions directly address the concern about potential correlations. revision: yes

  2. Referee: [Results] Main results (likely Table 2 or the regression reported in §4): the abstract states statistical significance and heterogeneity but the manuscript must report the exact sample size, the functional form of the peer-share variable, standard errors, and at least one robustness check (e.g., cohort fixed effects or alternative clustering) to allow evaluation of the magnitude and stability of the coefficient on Free-State share.

    Authors: We agree that greater transparency in reporting is essential. The revised paper now explicitly states the sample size for the main analysis. The peer-share variable is specified as the continuous proportion of Free State classmates in the graduating class. All regressions include robust standard errors, and we have added a robustness table that includes specifications with cohort fixed effects and clustering at the class level. These checks confirm that the main peer effect remains statistically significant and of similar magnitude. revision: yes

Circularity Check

0 steps flagged

No circularity: empirical identification relies on historical variation, not definitional reduction

full rationale

The paper is a purely empirical study that estimates peer effects via regression on historical West Point class composition data. The central claim rests on the identifying assumption that within-class variation in the share of Free-State cadets is quasi-random. No equations, fitted parameters, or self-citations are invoked to derive the reported effect; the result is an estimated coefficient, not a quantity forced by construction from the inputs. The derivation chain is therefore self-contained against external benchmarks and receives the default non-finding.

Axiom & Free-Parameter Ledger

0 free parameters · 1 axioms · 0 invented entities

The central claim rests on the assumption that classmate composition varies quasi-randomly and that peer exposure can be isolated from selection into classes.

axioms (1)
  • domain assumption The share of Free State cadets in a class is quasi-random conditional on observables and does not correlate with cadets' unobserved allegiance propensities.
    Invoked to identify causal peer effects from the abstract's description of leveraging quasi-random variations.

pith-pipeline@v0.9.0 · 5689 in / 1139 out tokens · 32092 ms · 2026-05-19T04:11:47.886438+00:00 · methodology

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Reference graph

Works this paper leans on

6 extracted references · 6 canonical work pages

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    [26]Hochschild, Arlie Russell.2016.Strangers in Their Own Land: Anger and Mourning on the American Right. New York: The New Press. [27]Jha, Saumitra, and Steven Wilkinson.2023. “Revolutionary Contagion.” Stanford University, Graduate School of Business. [28]Jones, Benjamin F, and Benjamin A Olken.2005. “Do Leaders Matter? National Leadership and Growth si...

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    The standard errors presented in the parentheses are obtained through bootstrapping with 400 resampling iterations

    Columns (1)-(3) focus on cadets from Slave States. The standard errors presented in the parentheses are obtained through bootstrapping with 400 resampling iterations. ***𝑝 <0.01, **𝑝 <0.05, *𝑝 <0.1. A-14 B.7 Peer Influence pre and post 1850 Table S10:Peer composition and allegiance choice before and after 1850 Dependent var Join the Union: war participant...

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