Importance Indices in Ethnobotany
Measuring the importance of plants and vegetation to people is a central concern in quantitative ethnobotany. A common tool to quantify otherwise qualitative data in the biological and social sciences is an index. Relative cultural importance (RCI) indices such as the use values developed by Prance et al. (1987) and Phillips and Gentry (1993a, 1993b) are applied in ethnobotany to calculate a value per folk or biological plant taxon. These approaches can provide data amenable to hypothesis-testing, statistical validation, and comparative analysis. The use of RCI indices is a growing trend in ethnobotanical research, yet there have been few attempts to compile or standardize divergent methods. In this review, we compare RCI indices in four broad categories and present a step-by-step guide to some specific methods. Important background topics are addressed, including ethnographic methods, use categorization, sampling, and statistical analysis. We are concerned here only with value as a non-monetary concept. The aspiring and veteran researcher alike should find this paper a useful guide to the development and application of RCI indices.