there. Originally developed in the agro-biological and then the medical sciences, impact evaluation (IE) methods have spread to the social sciences and are routinely employed in the areas of health and education. In essence, an impact evaluation compares the outcomes of entities — individuals or firms — that received support from a program or were directly impacted by a policy with the counterfactual outcome of those same entities had the program or policy not been in place. Because such counterfactual outcomes are not observable, they are approximated by the outcomes of a control group.

IE methods have provided powerful tools in other fields to help guide policy choices and minimize the cost of interventions. For instance, Banerjee and Duflo (2008) showed how a comparison of IE results established that, in order to raise school attendance rates among Kenyan children, a program to treat intestinal worms was twenty times more cost-effective than hiring teachers, suggesting a clear prioritization of actions.<sup>3</sup> The recent creation by the World Bank of a separate impact evaluation unit as part of the Development Impact Evaluation Initiative (DIME) has helped spread IE methods to new areas of development research and practice.<sup>4</sup> For instance, World Bank researchers have led the way in analyzing the impact of business registration reform or bankruptcy reform (Klapper and Love, 2010; Bruhn, 2011; Gine and Love, 2011). Researchers have also begun to use these methods to evaluate programs and policies in the area of private sector development, where the treated "entities" are firms (see McKenzie, 2010 for a survey). Similar evaluations could be used to guide trade interventions.

The usual excuse for _not_ using IE methods in assessing the effectiveness of trade assistance is that the "clinical" nature of the treatment needed for a proper definition of treatment and control groups is absent from trade policy. This was perhaps true of old-style trade policies like structural adjustment or tariff reforms; but it is not true of the new trade interventions like export promotion. This paper intends to show that _trade exceptionalism_ — the notion that trade-related interventions are inherently not amenable to IE — is, if anything, limited to traditional trade policies. More recent, focused trade-related interventions can be evaluated formally, provided that one is not wedded to a particular methodology such as randomized-control trials (RCTs). Although, as we will see, the range of application of RCTs is broader than one might think, other quasi-experimental methods are available and can shed light on what works and what does not.

> 3 This ratio was established by comparing the evaluation of a de-worming program by Miguel and Kremer (2004) with a separate evaluation of a program to reduce teacher-student ratios by Banerjee, Jacob, Kremer, Lanjouw, and Lanjouw (2005). Comparing impact estimates from separate impact evaluations is tricky since each has been established in a particular context with limited external validity (we will return to the issue later on in this paper). However, when the difference in cost effectiveness is as large as this one, the risk of getting the prioritization order wrong is reduced.

> 4 Information on DIME can be obtained at: http://web.worldbank.org/WBSITE/EXTERNAL/EXTDEC/ EXTDEVIMPEVAINI/0,,menuPK:3998281~pagePK:64168427~piPK:64168435~theSitePK:3998212,00.html.

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