Abstract
Ratio-type indices are often used to evaluate the residential environment of certain regions. This is because ratio-type indices are supposed to be free from the area of regions, and therefore it is believed that the values of indices can be compared among regions of different areas. Basically, similarity axiom is found to characterize these indices, implying that the accordance between the axiom and the feature to be measured justifies the usage of ratio-type indices. The general ratio-type indices are characterized by continuity axiom, monotonicity axiom and similarity axiom; and the simple ratio-type indices are characterized by continuity axiom, monotonicity axiom, similarity axiom, linearity-of-factor-2 axiom and linearity-of-factor-3 axiom. These results are also extended to additive-ratio indices.
