一、引言 20世纪50年代开始,三次产业的划分逐渐成为国民经济中通用的经济结构的分类和统计方法,并成为世界各国研究国民经济产业结构变动,了解经济发展水平,指导产业发展和制订产业政策的主要依据。随着信息时代的到来,知识经济和环境经 I. INTRODUCTION Since the 1950s, the division of the three industries has gradually become the classification and statistical method of the general economic structure in the national economy. It has also become a major issue for countries all over the world to study changes in the industrial structure of the national economy, to understand the level of economic development, to guide industrial development and to formulate industries The main basis for the policy. With the advent of the information age, knowledge economy and environment