HRDAG: Peruvian Truth and Reconciliation Commission’s Conflict Mortality Study

Reality and risk: A refutation of S. Rendón’s analysis of the Peruvian Truth and Reconciliation Commission’s conflict mortality study

by Daniel Manrique-Vallier and Patrick Ball, ‘Research and Politics,’ January-March 2019

Abstract
We refute S. Rendón’s recent criticism of the 2003 Peruvian Truth and Reconciliation Commission (TRC) conflict
mortality study. We first show that his most important result, an alternative estimate of the mortality due to the Maoist
guerrillas of Shining Path (Sendero Luminoso), is lower than existing observed data and is therefore impossible. We then
analyze his statistical approach and find that it is affected by a subtle form of selection bias. We contrast his approach to
the TRC’s using tools from statistical decision theory, and determine that his method is inadequate for this problem—
and that the TRC’s approach is, at minimum, better. Without advocating for the TRC’s original results, we conclude that
Rendón’s approach and methods are inferior to the TRC’s original work.

Introduction
Peru experienced a terrible internal armed conflict during the period 1980–2000 between the Maoist guerrillas of Sendero Luminoso (SLU) and agents of the Peruvian state (EST). In 2003, a team at Peru’s Truth and Reconciliation Commission (TRC) estimated conflict mortality due to violence using capture–recapture (CR) methods by combining the TRC’s information with five other databases. Estimates were stratified by location and perpetrator. Killings committed by SLU were infrequently documented by the nonTRC databases. Therefore, instead of obtaining direct CR estimates for SLU, the TRC first estimated a total including
both EST and SLU, then estimated EST alone, and estimated SLU by subtraction. Rendón (2019) disqualifies this procedure as “unusual,” and proposes instead estimating the few estimable strata and to extrapolate to the rest.

We agree that there are aspects of the TRC’s approach that should be improved—we have been working on this for several years. However, our response here focuses specifically on Rendón’s proposal: we show that his methods are substantially weaker than the TRC’s, and that his results are unsound…

Discussion
The TRC’s study has several limitations. In particular, estimates stratified by perpetrator require accounting for records with missing perpetrator labels, as Rendón does. In addition, we note that both the TRC’s estimates, and Rendón’s, rely on log-linear models which have important limitations (see e.g., Manrique-Vallier, 2016).

This said, existence of limitations in the TRC’s work does not by itself justify any alternative. Alternatives should at minimum stand on their own: they have to be statistically sound, and should produce plausible results. In addition, if they are to contribute anything to the discussion, they should also have some advantage over the original other than merely appearing more obvious. Rendón’s work fails all three of these requirements.

We agree with Rendón’s observation that the magnitude and distribution by perpetrator of killings during the Peruvian conflict are of great importance for Peruvian historical memory. We agree further that these questions merit considerable additional scientific attention. However, the flaws in Rendón’s
(2019) article make it unsuitable to this discussion.

Peru Conflict Mortality Manrique-Vallier Ball 2019

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