Longitudinal studies, such as the Young Lives study of childhood poverty, help us to analyse welfare dynamics in ways that are not possible using time-series or cross-sectional samples. However, analysis based on panel datasets can be heavily compromised by sample attrition. On the one hand, the number of respondents who do not participate in each round of data collection (wave non-response) will inevitably cumulate over time, resulting in falling sample sizes, which will undermine the precision of any research undertaken using such samples.

This article presents a framework for analysing the impacts of evidence-informed policy entrepreneurship, and applies it to a longitudinal policy research project on childhood poverty in the developing world. Drawing on insights from Keck and Sikkink's (1998) work on transnational advocacy, the discussion highlights five key dimensions of possible policy impact: framing debates and policy agenda formulation; securing discursive commitments from key policy actors; bringing about procedural changes; policy reform; and behavioural change.

The arguments in favor of trade liberalization are well known: it promotes the efficient allocation of resources through comparative advantage, allows the dissemination of knowledge and technological progress, and encourages competition. Trade liberalization is likely to have a major impact on the lives of poor children and their families. Although this effect may be positive in the long run, the development literature recognizes that it may have a negative short-run impact in sectors that are unable to adjust rapidly enough to the new policy context.