climatic stressors using the extensive data embedded in multi-topic and multi-purpose representative surveys should not be understated.

- We also highlighted that migration is not the only possible outcome of adverse weather events. From an empirical perspective, identifying people trapped in immobility in the aftermath of a shock is even more difficult than tracing induced mobility, especially in the absence of specific information on this provided by the affected household or individual.<sup>8</sup> While one can separately investigate effects on a welfare measure and, for example, indirectly argue that a reduction in consumption or assets, or an increase in liquidity constraints caused by a climatic factor may have prevented migration (see Hirvonen (2016) for an example of this approach), this may not necessarily have been the case, because the mediating role of the welfare measure is usually only indirectly and separately investigated. More generally, the empirical framework on the determinants of the “migration decision” could greatly benefit from the insights and models of the well-established literature on geographical and asset-based poverty traps (Barrett and Carter, 2013; Carter and Barrett, 2006; Carter et al., 2008; Jalan and Ravallion, 2002).

- <mark>Migration is not a random event, and weather- or climate-related migration is not an exception to this rule</mark> _<mark>.</mark>_ <mark>Self-selection comes into play when it comes to the decision to migrate or not (Carletto and De Brauw, 2012), be this decision due to climatic factors or not. Empirically, there are no clear prescriptions yet on how to address the self-selection-based endogeneity of migration,</mark><sup>9</sup> <mark>with the consequence that many research designs are neither robust nor reliable. Furthermore,</mark> since migration is intrinsically a selective process, any causal inference analysis needs to check for the determinants of migration and have access to the necessary information for the identification of

8 Incidentally, we also note that the immobility issue is not specific to climate-induced migration. It has long been known that immobility often masks the inability of people willing to move to do so, due to liquidity constraints, lack of information, absence of networks, etc. When these obstacles are removed, migration increases. A recent example of international migration triggered by a program aimed at fostering migration through improved connection and information about employment opportunities (carried out as part of an experiment implemented in Mizoram, India) is provided in Gaikwad, Hanson and Tóth (2022).

> 9 <mark>Although there is a wide set of technical alternatives that could be employed to address this key issue, including, but not limited to, two-phase sampling, Heckman selection, Instrumental Variables (IV) and data-driven statistical methods, there is often limited credibility of the exclusion restriction of the proposed instruments.</mark> New data mining techniques (e.g., LASSO variable and instrument selection) can help in addressing the identification challenges connected with migration by drawing on the vast potential and richness of information of multi-topic household surveys (see, _inter alia_ , Belloni et al., 2014).

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