Society is the union of every individual. The division of labor between people gradually became a collective division of labor within the process of social integration. If the successive emergence of the three industries in human history is the presentation of division of labor in the time dimension, the further development of collective division of labor into regional division of labor is the embodiment of division of labor in the space dimension. From Adam Smith to David Ricardo and then to Marx and Engels, looking at the views of famous political economists in history, we can find out in theory the factors affecting the division of labor.

First, as to the division of labor between areas, the degree of that depends on the factor endowment of local areas. The factor endowment contains all local natural conditions, such as natural resources, climatic conditions, production advantages brought by people’s traditions, and so on. From this point of view, this condition has considerable objectivity and rigidity. In other words, endowment, which is mainly based on natural conditions and traditional heritage, is difficult to be replaced and eliminated under some certain conditions. From David Ricardo’s Comparative Advantage Theory to Herschel Olin’s Factor Endowment Theory, classical economists try to explain the division of labor from the perspective of production factors and resource allocation. As David Ricardo mentioned in his book On the Principles of Political Economy and Taxation that the value of a commodity, or, in other words, the quantity of any other commodity it can be exchanged with, depends on the relative amount of labor necessary to produce it (Ricardo, 1962). The purpose of division of labor is exchange. They believed that when there are differences in resources, or factor endowments between cities, efficiency can be improved through division of labor and exchange. Based on this, the government should take the lead in coordinating the development space, make use of the advantages of local productivity to match the industry, and allocate the productivity and means of production appropriately.

Second, the degree of division of labor depends on the improvement of production efficiency that can be achieved as local production. Let’s take a look at Marx’s point of view. Marx believed that the reason for the formation of cooperation is that workers get rid of individual limitations and give full play to collective advantages and abilities in planned cooperation. Marx also believed that workers changed from independent workers to local workers in large-scale industrial production was one of the result of focusing on one job which improved the process and reduced non production costs. It was conducive to the improvement of production efficiency. On the basis of individual cooperation, Marx discussed the conditions and significance of urban-rural separation (Marx & Engels, 2012: p. 683). From individual cooperation, collective division of labor to regional division of labor, Marx believed that division of labor is a special kind of cooperation, and many of its advantages are produced by the general nature of cooperation.

Third, the degree of division of labor depends on the depth of exchange, that is, the degree of market development. Each part in the social economy produces products with comparative advantages due to its endowment in economic activities. Whether this product can be popular and realized its value in exchange needs to be solved by the market. For example, Adam Smith believed that division of labor comes from exchange, and the degree of exchange will also affect the degree of division of labor (Smith, 1972). In other words, the degree of division of labor in a country depends on the development of the market. If the market is too small, it is difficult to form a fine division of labor, and the expansion of the market between cities depends on the transportation cost.

Based on the research of political economists on the development of division of labor, these preconditions affecting division of labor were obtained, and the relevant theories on the layout of productivity were further obtained.

The emergence and development of urban division of labor stem from the diversification of material and cultural needs in the process of human development. Specialization brought by division of labor not only saves production costs in mass production, but also improves labor productivity, so as to promote the improvement of social productivity from the perspective of cost and efficiency. However, the specialized production under the division of labor will bring the problem of single product. The contradiction between the diversity of human material and cultural needs and the single product under specialized production always runs through the whole process of economic activities under the division of labor. The limitation of individual division of labor is solved by means of product exchange, which leads to the birth of “place” or “intermediary” of individual exchange, that is, the market. With the emergence of the market, people break the original “self-sufficiency” model and move towards the open state of product exchange. With the deepening of social division of labor, the society gradually moves from the original individual division of labor to regional division of labor and urban division of labor. At this time, the scope of social specialized production continues to expand, forming a model of orderly coordination within regions and rational division of labor among regions. Therefore, the diversification of human needs in daily life leads to the further development of exchange relations, and the need for exchange leads to the necessity of opening up.

The opening of cities will inevitably lead to further division of labor and specialization. Opening to the outside world will inevitably deepen the division of labor while deepening inter-regional relations. Opening to the outside world has strengthened the flow of production resources and the cooperation between social commodity markets. The production advantages of a certain region in the original relatively closed state may be difficult to highlight or even maintain its original advantages in the open economic system. Therefore, opening to the outside world means the expansion of the regional scope of coordination and division of labor. All regions must reposition according to their comparative advantages in the new and broader economy and find their own role in the new division of labor system. In this process, the degree of division of labor and specialization has gradually deepened, resulting in the flow of production factors and the progress of specialized production technology, which promote the development of regional economy. Therefore, opening to the outside world is bound to be accompanied by the deepening of division of labor and specialization. In order to occupy the advantages in the opening-up system and take advantage of the opening-up opportunities to promote self-development, cities must clearly position themselves and find the role that urban advantages can play in the division of labor system. The further opening of society has brought about the deepening of urban division of labor, which is the complementarity of the advantages of productivity and production factors at multiple levels and in multiple fields. In addition to economic and trade ties brought about by comprehensive opening-up, close ties have been established in many aspects, such as science and technology, social culture and ecological construction. Local history and culture, geographical resources and scientific and technological advantages will deeply affect the status and role of the region in the cooperative body, so as to deepen the level and system of urban division of labor and change the pattern of urban division of labor.

When examining the historical trend of Russian rural communes, Marx pointed out that Russia may not experience the stage of capitalist development under specific conditions and eventually move towards communism. This way is called “Crossing the Caudine Valley” (Marx & Engels, 2012: p. 825). This statement was named the Theory of Crossing the Caudine Valley. It was based on the fact that Russia had not experienced the full development of capitalism at that time, and the Russian commune still retained the basis of land public ownership. If Russia develops a public ownership society on the basis of this primitive organizational form, the Russian people can avoid experiencing this painful period of capitalist society. However, for the eastern countries that have not experienced the full development of capitalism, introducing and learning the economic elements that have been greatly developed in the capitalist society without changing their basic economic system is not only the inheritance and development of the common cultural wealth of human society, but also a way of exchanging space for time.

In the process of the development of modern urban communities, there is both the possibility of cooperation and the trend of competition among cities. Only by giving full play to their advantages in regional development and forming a unique urban division of labor system, can cities achieve regional coordinated development. Facing the world, China should take a new path of Chinese development and advocate the concept of coordinated development through consultation, joint construction and sharing. To achieve win-win results in urban and national cooperation, we must carry out division of labor and cooperation according to the production advantages of each region. Today, globalization has closely linked the fate of all countries in the world. Global economic cooperation is bound to achieve coordinated development in regional division of labor and common progress in complementary advantages. Therefore, we must study and layout according to the factors such as science and technology, resources and industrial foundation in urban development, improve our core competitiveness in the global economy while forming a reasonable division of labor mechanism, and provide Chinese solutions and Chinese wisdom for global governance.

The urban agglomeration in a region has gradually formed a stable division of labor system in a certain period of time. If the division of labor system and pattern of the region remain unchanged for a long time, can it achieve long-term sustainable economic growth? In fact, the objective conditions of regional development are dynamically adjusted with the interaction between external factors. The urban division of labor must change synchronously to meet the requirements of the development of productive forces. When we discuss the inevitability of the emergence of machinery and large industry, the workshop handicraft industry itself is developing continuously in the original division of labor system, which not only promotes the progress of productivity, but also affects the original division of labor structure. If the division of labor structure inside the workshop can no longer adapt to the advanced productivity at that time, that is, the machine mass production, this division of labor organization will gradually lag behind.

Therefore, in order to maintain the advantages of sustainable development, the urban division of labor system must constantly adapt to the requirements of advanced productive forces. Its essence is to constantly adjust and optimize the internal structure through the accumulation of knowledge and experience. How to make use of the urban division of labor to promote regional development? The key exist in the dialectical unity of contradictions between cities. No matter which aspect to see, the natural advantages or that of acquired, there are always relative differences between cities. That is to say, the struggle of contradictions between cities always exists. The differences show different forms in different times. In the period of relying on natural production, the advantage of natural or geographical resources is the dominant factor in inter-city differences; Nowadays, science and technology is the primary productive force. What’s more, science and technology and talent training have become the leading factors. Therefore, the basis of division of labor and coordination among cities has also changed. The reason why cities can divide labor and cooperate is that there is the basis for it, that is, the identity of contradictions. However, the existence of contradictory identity has a premise. If we can’t grasp the respective characteristics of cities, there will not be a unity. Therefore, the sustainable development of urban division of labor lies in following the pace of the times, constantly grasping the new situation and characteristics, and constantly improving the self revolution within the region.

With the regional development, cities will gradually shape their unique position in the regional division of labor system. For example, the city of Shenzhen used to be just a small fishing village in Guangdong Province. Under the system of reform and opening up, Shenzhen seized the opportunity to realize self-innovation. Now it has become one of the important areas driving economic growth in Guangdong and even the whole country. In order to achieve sustainable development in today’s globalization, Guangdong must learn and improve the ability in opening to the outside world, so as to continuously optimize its internal structure. Nowadays, the division of labor and coordination of Guangdong cities is essentially a process of absorption, sublation and reform in the open economy. The system and mechanism of division of labor have become the necessary basis for the development of the Great Bay Area. How to realize collaborative innovation under the premise of the differences between different systems and how to realize professional division of labor in today’s scientific and technological revolution are the problems that must be solved for the sustainable development of Guangdong-Hong Kong-Macao Greater Bay Area under the modern division of labor structure.

The industrial structure is the most basic structure in the regional economy, which reflects the internal connection between various industries in the regional economy. Therefore, comparing the changes of the industrial structure between regions, the development status and coordination of different regions and industrial developing situation can be analyzed. This paper applies the industrial structure similarity coefficient to quantify the industrial structure of the cities. The coefficient aims to measure the similarity of the industrial structure between the two cities. Based on the ratio of the three major department in the total output value, drawing conclusion through the inter-city relationship conjoint analysis of industry values. The industrial structure similarity coefficient provides data to support the further research on the industrial distribution and cooperation in the region, and show up a feasible plan based on the specific actual situation in the region.

In order to study the possibility and changes of the urban agglomeration of Guangdong in economic coordinated development, this paper selects the structural similarity coefficient proposed by the International Industrial Research Center of the United Nations Industrial Development Organization (UNIDO). (Qin & Pan, 2018) This index aims to study the degree of similarity or differentiation of the industrial structure in different regions. The higher the similarity coefficient, the more similar the industrial structures between the cities. The specific formula is as follows:

S i j = ∑ m X i m X j m ∑ m X i m 2 ∑ m X j m 2 (1)

The letter i and j represent two different regions, and m represents a certain industry, X i m is the proportion of the industry m in the industrial structure of region i. The index S i j is between [0, 1]. If it is 0, the industrial structure of the two regions is the same, and if it is 1, the industrial structure of the two regions is completely different at all.

For urban division of labor, the structural similarity coefficient itself only reflects the similarity of industrial distribution. The degree of similarity of industrial structure itself does not reflect the advantages and disadvantages of urban collaborative division of labor, but the distribution of different industries.

On the one hand, without understanding the structural similarity between cities, it is easy to cause the repeated waste of urban resources, vicious competition and monopoly, like those in some western society. In the free competitive market, capital expansion is carried out in the form of capital concentration and production concentration. Fierce competition leads to excessive resource concentration and investment in the same direction, and finally a monopoly situation is gradually formed through capital annexation. It makes the information mastered by a few people, and the use of resources is further limited. The repeated investment of resources will gradually reduce the social production efficiency. For the industrial structure between cities, there are many reasons for the high similarity of structural coefficient, one of which is the excessive concentration of resources in competition. Only by studying the similarity of industrial structure between cities can we have the possibility to know how the disorderly competition of cities causes the duplication of resources and then make timely adjustment at the macro level.

On the other hand, if we blindly pursue the similarity or difference of industrial structure, it is easy to be divorced from the actual social situation, resulting in the failure to achieve the expected economic and social effects of the government. The overall layout of urban division of labor should be an organic integration and should be based on following objective laws. It must be clear that the similarity coefficient of urban industrial structure is a number and the internal reasons for its formation are diverse. The higher similarity coefficient of industrial structure does not mean that the possibility of industrial development synergy between cities is low. Similarly, if regional industries are complementary and can develop together, it may also show that the similarity coefficient of industrial structure tends to be lower. Take the second industry as an example. If the structural similarity coefficient tends to be higher, it may suggest that the regional urban agglomeration is suitable for the development of the secondary industry especially manufacturing industry, while industries in different cities form complementary and coordinated development among the subdivided industries. The same is true when it comes to the low coefficient of structural similarity. For example, the low structural similarity coefficient of an urban agglomeration may be due to the different conditions and backgrounds of each city, which can get complementary development in modern agriculture, service industry and other fields.

Therefore, the similarity coefficient of industrial structure is only an entrance to the analysis in the construction and planning of urban division of labor system. The simple number itself cannot be used as the direct judgment basis for the layout of urban collaborative division of labor. Jumping out of the number itself and finding the reason behind the coefficient is the fundamental method for the construction and development of urban division of labor system. All social development should follow objective truth, and the so-called objective truth is the unity of regularity and purpose. Following the objective figures to find the reasons for the development status of industrial structure among cities, and fully understanding the history and objective conditions of urban development have become the basic clue to investigate and obtain more information.

Because the COVID-19 began in December 2019, the year 2019 is the last year for the world economy to operate under normal conditions before the epidemic. Based on the statistical yearbook of Guangdong Province, this paper selects the data of the proportion of three industries in various cities of Guangdong Province from 2015 to 2019 for statistical analysis, and studies the change trend of the similarity coefficient of industrial structure in the 5 years. The similarity coefficients of industrial structure between cities are as follows¹:

The above chart shows that the change of industrial structure similarity coefficient of cities in Guangdong Province is relatively stable. For example, taking the industrial structure of Guangzhou as a reference, the similarity of industrial structure between Shenzhen and Guangzhou is high. The similarity coefficient of industrial institutions remains between 0.96 and 0.99. And, the similarity of industrial structure between Foshan and Guangzhou is relatively low, always lower than 0.85. The industrial structure of Shenzhen has changed significantly in the past five years, which should be related to the construction of Guangdong-Hong Kong-Macao Great Bay Area (GBA).

Taking five years as a research period, this paper compares the industrial structure similarity coefficients between cities in Guangdong Province at both ends of this time period, that is, 2015 and 2019, as shown in Graph 1 and Graph 2 below. Graph 1 and Graph 2 show the coefficients between Guangzhou and Shenzhen and other Guangdong cities in 2015 and 2019 respectively; Graph 3 shows the change of structural similarity coefficient between Guangzhou, Shenzhen and other cities in Guangdong Province in the 5 years²: