rank-size rule
noun[S]
ECONOMICSukus(alsorank-size law,rank-size distribution)theprinciplethat many things all over theworld, forexamplethesizesofcitiesorbusinesses, or howrichpeopleare,followthe samepatterninrelationtotheirrankon alist:
According to the rank-sizerule, arank3citywould have ⅓ thepopulationof a country'slargestcity, arankfourcitywould have ¼ thepopulationof thelargestcity, and so on.