to a permanent loss of stature of 2.3 cm on average. Other long-term negative effects include a delay in starting school by 3.7 months and a decline in completed years of schooling by 0.4 years. According to the authors, these effects altogether result in an average reduction in lifetime earnings of 7 percent. Being in a vulnerable age group at the time of a shock can affect a child’s lifetime welfare whether or not the household's income recovers from the shock.

This paper reviews 29 studies and summarizes their findings on the effect of covariate shocks on the nutrition status of children below age five in developing countries. The paper also reviews the findings on some specific sub-questions, namely the pathways through which shocks may affect child nutrition status, the relationship between the timing of exposure to a shock and the shock’s effect on child nutrition status, the potential mitigating role of public interventions on the negative effect of shocks on child nutrition status, and on the long-run persistence of effects and potential catch-up growth.

The different child nutrition indicators examined in the review comprise height-for-age z-scores (HAZ), the probability of stunting status, weight-for-age z-scores (WAZ), the probability of underweight status, weight-for-height z-scores (WHZ), and the probability of wasting status.<sup>1</sup> The review also examines child micronutrient deficiency, which can impair growth and development, weaken immunity, and increase the severity of illness.

Covariate shocks comprise extreme events such as natural disasters, civil war, and economic crisis, as well as anomalies in rainfall and temperature compared to historical means. Given the diversity of shocks and outcome measures in the reviewed papers, we opt for a narrative review of the evidence rather than a formal meta analysis.

To our knowledge, this is the first attempt to systematically review the evidence on covariate shocks and child nutrition status in developing countries. Studies that test for household-level consumption insurance have traditionally served as the basis for public policy recommendations. However, a stronger case can be made for public intervention based on evidence on the intrahousehold effects of covariate shocks, and particularly the effect on the nutrition status of children, given the high, long-term economic costs of poor child nutrition status to both the individual and society. By summarizing what has been researched and what has not, where the evidence is more consistent and where it is less so, the paper aims to provide guidance to researchers. Based on the patterns in the findings and insights gleaned from the review, the paper also aims to inform the choice and design of public interventions that can help mitigate the negative effect of shocks on child nutrition status, especially in developing countries.

The remainder of the paper is organized as follows. Section II describes the literature search and results. Section III provides definitions of shocks in the reviewed studies. Section IV discusses findings on the effect of covariate shocks on child nutrition status. Section V discusses the potential

> 1 Stunting, wasting, and underweight statuses are defined as HAZ, WHZ, and WAZ less than 2 standard deviations (SD) below the relevant WHO Growth Standards medians, respectively. Stunting status (low height-for-age) is considered to reflect chronic undernutrition due to inadequate food intake over the long term, or repeated or chronic illness. Wasting status (low weight-for-height) is considered to reflect acute undernutrition due to a recent drop in food intake or recent acute illness. Underweight status (low weight-for-age) is a hybrid measure of height-for-age and weight-for-height, and thus considered to reflect both acute and chronic undernutrition (de Onis and Blossner 2003).

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