Investment climate reforms may not always be amenable to (or even appropriate for) impact evaluation methods that have risen to prominence in recent years, such as randomized controlled trials (RCTs) and quasi-experimental methods.<sup>3</sup> The nature of the interventions can involve challenges in identifying or distinguishing among different types of firms; reforms may be implemented at the national level or to specific sectors, making comparisons or construction of counterfactuals difficult (if not impossible); capturing changes in firm behavior as a response to reforms might involve a long causal chain of observable and unobservable processes. In the face of such challenges, the integration of qualitative and quantitative methods (i.e., using mixedmethod approaches) can be a constructive, pragmatic response to the challenges of conducting impact evaluations: helping to identify appropriate counterfactuals, to assess the efficacy of causal links and processes, and to guide decisions about the wisdom of cancelling, continuing or scaling up an intervention, or replicating it elsewhere.

Although there are increasing calls to recognize the shared and complementary roles of qualitative and quantitative research methods<sup>4</sup> , for present purposes it is helpful to begin with their respective core strengths and characteristics. Where quantitative research methods include econometrics, experiments and mathematical modeling based on numerical data drawn from surveys and official accounts; qualitative research methods include case studies, process tracing, and ethnography, which draw on data derived from in-depth interviews, focus groups, participation, observation, historical documents, media images, and texts. However, qualitative data are increasingly being quantified. For example, due to recent advances in computing power, it is now possible to scan huge volumes of text to discern patterns with regards to (say) the changing incidence and meaning of key words<sup>5</sup> , and to incorporate questions capturing subjective perceptions into large-N household surveys. Similarly, some anthropologists also engage in experimental studies (Ensminger, 2000), while comparative political scientists often

> 3 An RCT (randomized controlled trial) randomly assigns a pre-determined fraction of eligible project beneficiaries to receive the project; such beneficiaries are called a treatment group. The remaining eligible beneficiaries do not receive the project, and thus comprise the control group. The difference in outcomes between the treatment and control group is the impact of the project. A quasi-experimental method constructs a comparison group when it is not possible (for political, ethical, financial or logistical reasons) to randomly assign groups.

> 4 The word “methods” is used here to refer to the various techniques used for conducting evaluations, including the design, collection, analysis and interpretation of data. For a more nuanced view, see Hentschel’s (1999) useful distinction between methods and data in development research.

> 5 Ravallion (2012), for example, analyzes the changing frequency with which the word ‘poverty’ has appeared in all printed English-language documents (that are available on-line) published since 1800.

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