When the senior statesmen system was first introduced, a senior statesman was defined as 'persons who had been granted the privileges of his former post as Prime Minister as well as the Chairman of the Privy Council'; however, in1940 the definition was revised to simply 'former Prime Ministers and the Chairman of the Privy Council.'
制度導入当初は、重臣とは「内閣総理大臣の前官礼遇を賜りたる者及び枢密院議長」であったが、1940年に単純に「首相経験者及び枢密院議長」に改正された。