芦叶满汀洲,寒沙带浅流。二十年重过南楼。柳下系船犹未稳,能几日,又中秋。岭外音书绝,经冬复立春。If productivity measures the efficiency of an economy, a measure of what an economic system produces is its gross national product (GNP), which is the current market value of all final goods and services that a nation produces within a particular period. |