A measurement of the degree of concentration of a given phenomenon, such as industry, over a set of regions (also called the index of concentration). Values of the coefficient, L, lie between 0 (even distribution) and 1 (extreme concentration). Lafourcade and Mion (2007) Reg. Sci. & Urb. Econ. 37, 1 use the coefficient to study the geographic distribution of manufacturing and the size of plants.