Looking at 99 countries since 1980 , mehmet caner and thomas grennes of north carolina state university with fritzi koehler-geib of the world bank identified a threshold of 77 % of gdp .

来自北卡莱罗纳州立大学的mehmetcaner和thomasgrennes与世界银行的fritzikoehler-geib回顾了1980年以来99个国家的情况，确定gdp的阈值为77%。