Tucker and Townshend (2000) conclude that wall-to-wall coverage is needed to avoid gross errors in estimations of deforestation rates' because tropical deforestation is concentrated along roads and rivers. They specifically question the reliability of the 10% sample of Landsat sensor scenes used in the global remote sensing survey conducted by the Food and Agricultural Organization (FAO) of the United Nations. They base their conclusion on simulations with data from Bolivia, Columbia and Peru, in which the size of a 10% sample is 4 less-than or equal to n less-than or equal to 6 Landsat sensor scenes. However, their conclusion is not valid when extrapolated to larger sample sizes (e.g. n greater-than or equal to 40), such as those employed by the FAO and the European Commission for global and pantropical assessments.