Constructed by N. Ramankutty, J.A. Foley, J. Norman, and K. McSweeney. Downloadable as part of Global Land Use Database.
The unit of observations is the 0.5 by 0.5 degree grid cell. For each cell, this raster data provides the fraction of cell areas that is cultivable. According to Michalopoulos (2007, p. 18), this dataset is constructed by "(i) empirically fitting a relationship between existing croplands and both climate indices and soil characteristics and then (ii) combine the derived relationship with the available regional climatic and soil characteristics to predict the regional suitability of agriculture worldwide."
Used by Michalopoulos (2007) "Ethnolinguistic Diversity: Origins and Implications" to measure the variation in land quality in a given area.