Study area: Guangdong-Hong Kong-Macao Greater Bay Area

The GBA megacity region, located in southern China, is selected as the study area. The GBA megacity region consists of 9 cities, namely, Guangzhou, Foshan, Zhaoqing, Shenzhen, Dongguan, Zhuhai, Jiangmen, Zhongshan and Huizhou, as well as 2 special administrative regions, namely, Hong Kong and Macao (shown in Fig 1). The GBA encompasses the main area of the Pearl River Delta and is considered one of the most important components of the world-class urban agglomeration in China and in enabling the country’s participation in global competition. With a total area of 56,000 square kilometers, the GBA is the fourth-largest megacity region in the world, after the New York Bay Area and the San Francisco Bay Area in the United States and the Tokyo Bay Area in Japan [34]. In 2018, the total population of the GBA reached 70 million; additionally, its GDP exceeded 10 trillion yuan, accounting for 12.17% of the national economy. The total GDP of this region ranks 11th in the world.

Fig 1

Location of the GBA in China.

Reprinted background map from the National Catalogue Service for Geographic Information (www.webmap.cn) under a CC BY license, with permission from the National Geomatics Center of China, original copyright 2020.

Data sources from 2000 to 2018

Statistical data corresponding to nineteen periods from 2000 to 2018 are selected for analysis. The total population index is used to represent the number of people in the area, the regional GDP indicator is used to represent economic development, and the total retail sales of social consumer goods is used to represent the consumption level. These statistics are taken from the annual data analysis of China Economic and Social Big Data Research Platform (http://data.cnki.net/YearData/Analysis), the National Bureau of Statistics of China (http://www.stats.gov.cn/tjsj/), the Statistics Department of the Government of the Hong Kong Special Administrative Region (https://www.censtatd.gov.hk/), the Statistics and Census Bureau of the Government of the Macao Special Administrative Region (https://www.dsec.gov.mo/zh-MO/), and the statistical yearbooks and bulletins of each administrative region within the GBA for the relevant years. The monetary units of the Hong Kong and Macao economic statistics have been converted into RMB units according to the average exchange rate data at the end of each quarter of each year, in which the exchange rate data come from the China Foreign Exchange Trading System-National Interbank Funding System (http://www.chinamoney.com.cn/), and the State Administration of Foreign Exchange (http://www.safe.gov.cn/). It should be noted that as some changes have taken place in the administrative districts in the GBA since 2000, some statistical data are missing in these changing districts. Thus, biases could exist in calculating city-level or even smaller-scale socioeconomic indicators during the period of 2000–2018.

As shown in Fig 2, the socioeconomic indicators of the GBA changed dramatically from 2000 to 2018. The population of the GBA increased from 49.99 million in 2000 to 71.09 million in 2018. During the 18 year period, the total population of the area increased by 21.1 million, with an average annual increase of 1.17 million. In 2018, the GDP of the GBA reached 10,865.84 billion yuan (5.38 times that of 2000) and exhibited an average annual growth rate of 24.31%. The total retail sales of social consumer goods in the GBA reached 3,364.25 billion yuan in 2018 (7.88 times that of 2000) and exhibited an average annual growth rate of 38.2%; this growth rate was higher than that of the regional GDP for that year.

Fig 2

The development of the population, GDP and total retail sales of the GBA from 2000 to 2018.

Spatiotemporal interactions among the individual cities

The regional differences in terms of the three socioeconomic indicators, namely, GDP, total retail sales and population, are involved in the exploration of the spatiotemporal interactions between the individual cities. Both the growth values and the growth rates of these three indicators are considered when detecting the changes in various trends; subsequently, the similarities among the indicators of the different cities are quantified using a hierarchical clustering method.

To detect the changes in the trends of the socioeconomic indicators, this paper presents their growth values and growth rates with a linear graph and a cumulative percentage histogram; in the graph and the histogram, the growth values of the indicators are depicted annually, and the growth rates correspond to four periods, namely, 2000–2005, 2005–2010, 2010–2015 and 2015–2018. To quantify the similarities among the cities, the hierarchical clustering method is adopted in this paper. First, the indicators are subjected to z standardization processing to eliminate the influence of dimensional and order-of-magnitude differences among them on the calculation results. Then, the temporal similarities among the socioeconomic indicators are defined as the distances between the clusters obtained through the hierarchical clustering method; these distances are calculated using the square European distance as follows:

Spatiotemporal changes in the entire megacity region

The spatiotemporal changes within the entire megacity region are investigated by analyzing the gravity centers of the socioeconomic indicators and identifying their gravity center paths. In particular, the gravity centers of the socioeconomic indicators are detected by delineating the locations of the gravity centers and the characteristics of the spatial distributions, while the gravity center pathways are identified by determining their directions and lengths.

Gravity center detection

Spatial distribution of the gravity centers. The term gravity center refers to the various points in an object generated by the gravity [35]; this factor is calculated as the average value of the geometric coordinates of all the cities in a region [36]. In this way, the socioeconomic indicators of the area are employed to derive the gravity centers of GDP, total retail sales and population. This modified method quantifies the value of each of these attributes within each city and uses these values as weights to calculate the weighted regional average gravity center of the three indicators as follows [34]:

where n is the total number of cities in the study area, and x_i and y_i are the longitude and latitude coordinates, respectively, of the i-th city. p_i is the quantified value of the i-th city, and X and Y are the coordinates of the gravity centers corresponding to GDP, total retail sales and population.

Spatial distribution of the standard deviation ellipses. Based on the calculated gravity centers, standard deviation ellipses (SDEs) are applied to reveal the spatial distribution characteristics of the gravity centers in terms of the spreading range, dispersion, direction and shape; this calculation is as follows [37]:

where $$ \overline{X_w}$$ and $$ \overline{Y_w}$$ represent the center of a spatial distribution, $$ \overline{x_i}$$ and $$ \overline{y_i}$$ represent the relative coordinates of the i-th coordinate point from the gravity center of the spatial distribution, and n is the total number of cities. The weight is represented by w_i. This paper takes the population, GDP and total retail sales of each city as its weights. The azimuth angle of the SDE is represented by θ; this indicates the angle formed by the long axis of the SDE when it is rotated clockwise from the positive north direction. The lengths of the x and y axes of the SDE are represented by σ_x and σ_y.

Gravity center pathway analysis

Direction of gravity center movement. The population, GDP and total retail sales in the region are constantly developing and changing. If the development of a certain factor in the region is not balanced, the regional gravity center of that factor will move in the direction of "high density"; its direction angle is then calculated as follows [38]:

where the correction coefficient n is (0, 1, 2); x_k+1−x_k and y_k+1−y_k represent the changes in the longitude and the latitude of the barycenter coordinate between the k−-th year and the k+1 year, respectively; and θ_(k+1)−k represents the change in the barycenter movement angle (−180° ≤ θ ≤ 180°) between the k-th year and the k+1 year. When θ = 0°, the gravity center moves due east. When θ = 180°, the gravity center moves in the positive west direction. When 0° < θ < 90°, the gravity center moves toward the northeast. When 90° < θ < 180°, −180° < θ < −90° and −90° < θ < 0°, the gravity center moves toward the northwest, southwest and southeast, respectively.

Distance of gravity center movement. The distance of the gravity centers’ movement represents the degree of the changes that occurred in the regional factors of each city during a certain time period; this is jointly determined by these factors’ development within all the cities of the research area. The calculation of this distance is as follows [29]:

Where C is a constant equal to 111 km that represents the coefficient of conversion from the coordinate unit of the earth's surface (degree) to the plane distance (km); X_k+1−X_k and Y_k+1−Y_k and represent the changes in the longitude and the latitude of the gravity center coordinates between year k and year k+1, respectively; and d_(k+1)−k represents the distance that a gravity center moved between year k and year k+1.

Contributions of major cities

To explore the influence of different cities on the overall regional differences, this paper compares the net growth of the three indicators within the different cities of the GBA in 2018 with the net growth of the same indicators in 2000; additionally, it analyzes the contribution of each city during different periods. The socioeconomic contribution model enables the direct separation of a specific socioeconomic index from the overall economic growth of an area [39]. It is utilized to separately identify the contribution of each city and evaluate this contribution in terms of the overall development of a megacity region. The calculation is as follows:

Spatiotemporal evolution among the individual cities

Changes in the population, GDP and total retail sales trends of the individual cities

As shown in Fig 4(A), Guangzhou and Shenzhen had the largest populations from 2000 to 2018; Dongguan, Hong Kong and Foshan followed these areas in terms of population, and the other cities including Huizhou, Jiangmen, Zhaoqing, Zhongshan, Zhuhai and Macao, had relatively small populations. In terms of economics and consumption levels, the different cities show similar growth characteristics. Guangzhou, Shenzhen and Hong Kong exhibit the highest levels of economic and consumption development. Foshan and Dongguan are second in terms of this development, while the remaining cities including Huizhou, Zhongshan, Macau, Zhuhai, Jiangmen and Zhaoqing, rank third. Due to the differences in the population carrying capacities and economic carrying capacities among the different regions, the absolute value gaps between the social development indicators of the different regions within the GBA widened during the past 18 year period.

Fig 4

The changes in (a) and growth rates of (b) the populations, GDP and total retail sales of the different cities.

The changing trends of the growth rates can be clearly observed in Fig 4(B). From 2000 to 2018, the cities in the GBA achieved positive population growth. Among them, Shenzhen has the highest population growth rate, proving its strong demographic appeal. The population growth rates of Jiangmen, Zhaoqing, and Hong Kong are much lower. Obviously, these three cities are not preferred places for the migrant population. Except for Hong Kong, the overall differences in the growth rates of GDP and total consumption of each city from their original basis are not obvious. The reason that Hong Kong exhibits a lower development speed is that its original economic and consumption levels are higher; thus, it has less room to increase than other cities do, which explains the slower rate of Hong Kong's development and the rapid advancement of the other cities in the area. However, Hong Kong still plays a strong leading role among these cities.

Similarity of spatiotemporal evolution

The results of the hierarchical clustering method are shown in Table 1 and Fig 5. Specifically, the entire GBA megacity region can be divided into two categories as follows: Guangzhou, Shenzhen, and Hong Kong can be placed in a category corresponding to a high level of development, and the other nine cities can be categorized as relatively underdeveloped in terms of population, GDP and total retail sales. According to the different modes of urban socioeconomic development, when the square Euclidean distance is 4, these cities can be further divided into four non-ranking categories, as follows: Hong Kong is placed in its own category, as it has a high starting point and a low growth rate; Guangzhou and Shenzhen are placed in the second category, which is characterized by high starting points and high growth rates; Dongguan and Foshan are placed the third category, which is characterized by low starting points and high growth rates; and the remaining six cities belong to the fourth category, which is characterized by low starting points and low growth rates. The fourth category can be further subdivided into categories containing 1) Macao and Zhuhai and 2) Zhongshan, Zhaoqing, Huizhou, and Jiangmen.

Fig 5

Tree diagram of the hierarchical clustering analysis.

Table 1

Hierarchical clustering results.

Stage	Cluster Combined		Coefficients	Stage Cluster First Appears		Next Stage
	Cluster 1	Cluster 2		Cluster 1	Cluster 2
1	5	7	0.500	0	0	2
2	5	6	1.301	1	0	5
3	3	11	2.322	0	0	6
4	4	9	3.142	0	0	8
5	5	8	3.317	2	0	6
6	3	5	14.305	3	5	8
7	1	2	24.583	0	0	9
8	3	4	45.202	6	4	10
9	1	10	86.162	7	0	10
10	1	3	224.905	9	8	0

The classification of the individual cities based on the above spatiotemporal similarity patterns is shown in Fig 6. Cities with similar patterns in terms of population, GDP, and total retail sales are classified into one category. Guangzhou, Shenzhen, and Hong Kong, which are the three developed cities, are naturally separated from the other cities by virtue of their large populations and GDP volumes. Because the development speed of Hong Kong's three indicators is obviously different from that of the indicators of Guangzhou and Shenzhen, Hong Kong will be separated from these two cities when the cities are further subdivided. Dongguan and Foshan are the second-class cities in the GBA, and their development characteristics are also different from those of the remaining cities. Overall, the clustering results effectively classify each individual city and show that some of the cities in the GBA exhibit the same development characteristics as others.

Fig 6

Classification of the urban development characteristics of the cities in the GBA.

Reprinted background map from the National Catalogue Service for Geographic Information (www.webmap.cn) under a CC BY license, with permission from the National Geomatics Center of China, original copyright 2020.

Spatiotemporal evolution of the entire megacity region

Spatial distribution patterns of the gravity centers

As shown in Fig 7, compared with the geographical coordinates of the geometric center of the GBA in the Panyu District of Guangzhou, Guangdong, the population gravity centers of the GBA for the time period from 2000 to 2018 is located in Shatian Town of Dongguan; the GDP gravity centers for the same time period is located in the Bao'an District of Shenzhen; and the gravity centers of total retail sales for this time period is located in Humen Town of Dongguan. Assuming that the average gravity centers are independent points, starting from the geometric center of the area and traveling southeast, one would pass through the average gravity center of the population, then the average center of total retail sales, and finally the average center of GDP. From 2000 to 2018, the population gravity center, GDP gravity center, and total retail sales gravity center of the GBA did not coincide with the regional geometric center of the area. These three gravity centers remained southeast of the regional geometric center during that time period and are different average distances from the geometric center. This shows that the regional population, GDP and total retail sales of the GBA are unevenly distributed. Among these factors, the GDP of the area shows the highest degree of imbalance, followed by total retail sales and population. The three gravity centers are all located east of the regional geometric center, indicating that the eastern cities of the GBA have higher population densities, GDP and total retail sales than the western cities.

Fig 7

Gravity centers and SDEs of the population, GDP and total retail sales of the GBA.

Reprinted background map from the National Catalogue Service for Geographic Information (www.webmap.cn) under a CC BY license, with permission from the National Geomatics Center of China, original copyright 2020.

The SDEs further illustrate the degree of imbalances among the three indicators. Specifically, the distributions generally trend in the direction of "southeast-northwest"; additionally, their azimuth angles mainly range between 102 and 125 degrees, and they are all greater than 90 and less than 135. This shows that the population, GDP and total retail sales in the east-west direction are slightly higher than those in the north-south direction; this trend is also related to the shape of the GBA. During the 18 year period studied, the SDE of the population pattern in the GBA remained relatively the same, while the SDE of the GDP pattern and the total retail sales pattern clearly moved toward the northwest. From the evolutionary trend in terms of the long and short axes of the SDE, it can be observed that the lengths of the long and short axes of the population pattern SDE are decreasing; that is, this SDE are shrinking toward the central city. However, the lengths of the long and short axes of the GDP pattern SDE show an increasing trend that is the opposite of the population pattern, indicating that the economy of the GBA expanded from 2000 to 2018 but that the population was more concentrated during that time.

Evolutionary process of the three gravity centers

From 2000 to 2018, the geographic coordinates of the population gravity center ranged from 113°34′17″ to 113°36′4″E and from 22°52′4″ to 22°53′15″N, all located in Dongguan. Compared with its location in 2000, the population gravity center had moved 3.34 kilometers to the northeast by 2018. It further deviated from the geometric center of the region in terms of longitude and latitude. In general, the evolution of the population gravity center of the GBA from 2000 to 2018 can be divided into a large-scale phase of movement from 2000 to 2010 and a small-scale phase of movement from 2010 to 2018. During the former stage, the gravity center of the population moved to the southeast and then to the northeast, exhibiting a “V” shape. During the latter stage, the gravity center of the population moved eastward, and the magnitude of this movement was significantly smaller than that of the former stage. During this period, the maximum range of movement exhibited by the population gravity center was 2.42 kilometers northeast from 2005 to 2010.

During the 18 years studied, the geographical coordinates of the GDP gravity center ranged from 113°44′21″ to 113°53′45″E and from 22°36′38″ to 22°47′34″N and were located in Dongguan and Shenzhen. Compared with its location in 2000, the GDP gravity center had moved 24.95 kilometers to the northwest by 2018. By the end of the study period, it was far from the regional geometric center in terms of latitude and longitude. In general, the evolution of the GDP gravity center of the GBA from 2000 to 2018 can be divided into a large-scale phase of movement from 2000 to 2010 and a small-scale phase of movement from 2010 to 2018. During the former stage, the northwestern movement of the GDP gravity center was obvious. During the latter stage, the movement range of the GDP gravity center decreased, and its direction of movement shifted to the northeast. During this period, the maximum range of movement exhibited by the GDP gravity center was 13.34 kilometers northwest from 2000 to 2005.

The geographical coordinates of the total retail sales gravity center ranged from 113°39′3″ to 113°46′26″E and from 22°45′24″ to 22°52′44″N, all located in Dongguan. Compared with its location in 2000, the total retail sales gravity center had moved 10.1 kilometers to the northwest by 2018. By the end of the study period, it was closer to the regional geometric center in terms of longitude and latitude. The overall movement of the total retail sales gravity center is similar to that of the GDP gravity center; additionally, it shows a clear trend toward the northwest. During this period, the maximum range of movement exhibited by the total retail sales gravity center was 6.61 kilometers to the northwest from 2005 to 2010.

After decomposing the geographical coordinates of the population gravity center, the longitude and latitude of the GDP and total retail sales gravity centers for each year are calculated as shown in Fig 7 to intuitively explore the changing characteristics and the correlations among the different directions of these three factors’ movements, as shown in Fig 8. Since 2000, the population gravity center of the GBA has generally moved away from the geometric center of the region and has shifted northeast. The GDP gravity center and the total retail sales gravity center show a tendency to approach the geometric center of the region. Compared with their location during the initial stage of the study period, both shifted to the northwest. The latitude range of the population gravity center is close to that of the total retail sales gravity center, and the movement trajectories of the two are convergent.

Fig 8

Comparison of the latitudes and longitudes of the population, GDP and total retail sales gravity centers in the GBA.

From 2000 to 2018, the population gravity center in the GBA moved a total of 5.37 kilometers, the GDP gravity center moved a total of 27.41 kilometers, and the total retail sales gravity center moved a total of 39.19 kilometers. In particular, the total retail sales gravity center shows the highest level of movement in the GBA, followed by the GDP and population gravity centers. This indicates that the total retail sales gravity center fluctuates the most, followed by the GDP gravity center; however, the population gravity center is relatively stable.

The contributions of major cities to the regional differences in the GBA

During the 18 years studied, among the nine cities and the two special zones in the GBA, Shenzhen has experienced the largest population increase, with a total increase of 6.01 million people. As shown in Fig 9, Shenzhen also experienced the highest increase in GDP, with a total increase of 2,200.278 billion yuan. Finally, Guangzhou shows the highest increase in total retail sales over this period, with a total increase of 813.506 billion yuan. Overall, Guangzhou and Shenzhen played leading roles in the regional development of the GBA over the 18 years studied. Due to the differences in the development speeds of the various cities in the region, as well as their different populations and economic carrying capacities, the gaps between the absolute values of the social development indicators of the different cities in the GBA widened from 2000 to 2018.

Fig 9

Net increase in the population, GDP and total retail sales of the GBA (2018 vs. 2000).

Reprinted background map from the National Catalogue Service for Geographic Information (www.webmap.cn) under a CC BY license, with permission from the National Geomatics Center of China, original copyright 2020.

To determine which city contributes the most to the movement of the gravity centers, this paper employs statistical data to calculate the contribution of each city to the movement of the different gravity centers during the 2000–2018 period. The results of this analysis are shown in Fig 10. In this rose plot, the length of the color band represents the contribution of the city. Over the 18 years studied, the contribution of the western cities in the GBA to the movement of the population gravity center was less than that of the cities in the central and eastern regions. Among them, Guangzhou and Shenzhen exhibit the highest population increases, followed by Foshan, Dongguan and Huizhou; however, Zhaoqing, Jiangmen, Zhuhai and Zhongshan exhibit the lowest population increases. Since China's reform and opening up, Guangdong has attracted a large number of migrants from the mainland to work in the city and has become a famous manufacturing base. However, due to differences in their administrative systems, economic systems, financial systems, currency systems, etc. [40], as well as their limited land area and high-density population, Hong Kong and Macao do not have much potential to attract large number of mainland Chinese people to live and work there. Therefore, a significant trend in population growth is not observed. In terms of these cities’ contributions to the movement of the GDP and total retail sales gravity centers, three cities of the GBA clearly contribute the most. Guangzhou, Shenzhen and Hong Kong dominate the movement of the GDP and total retail sales gravity centers. Foshan and Dongguan also play important roles, while Zhuhai, Jiangmen, Zhaoqing, Huizhou, and Zhongshan contribute less. Macao’s contribution to the movement of the GDP and total retail sales gravity centers is also small due to its limited economic carrying capacity.

Fig 10

The contribution of each city to the movements of the gravity centers.

Discussion of three types of gravity center movement characteristics in the GBA

According to the findings above, the population gravity center gradually moved eastward from 2000 to 2018. As they are first-tier cities of China, Guangzhou and Shenzhen have high-quality social resources and can attract people from all over the country. Dongguan, as it has the advantage of being close to Shenzhen and Hong Kong, has built a globally competitive low-cost industrial zone, thus becoming a "world factory" and attracting a large number of interprovincial floating populations [41]. Huizhou, due to its good environment and low cost of living, has a higher mobility tendency than Shenzhen; thus, it has accommodated the housing needs of some Shenzhen workers. In contrast, the western region lacks leading cities; Foshan’s population contribution is not as advantageous as that of the cities in the eastern region, and it does not have enough power to pull the center of population toward the west. It should be noted that the population, GDP and total retail sales gravity centers are related to the regional average centers instead of the absolute higher values.

With regard to the changing trends exhibited by GDP and total retail sales, the GDP and total retail sales gravity centers show similar spatiotemporal trends; both moved significantly northwestward during the 2000–2018 period [42, 43]. Specifically, the GDP gravity center was far from the regional geometric center in 2000 and was very close to Hong Kong. In fact, Hong Kong’s GDP was in an absolute leading position in the GBA in 2000; its GDP was 4.5 times that of Guangzhou and 5.1 times that of Shenzhen. However, from 2000 to 2018, Hong Kong’s GDP increased at a much slower rate. Shenzhen overtook Hong Kong in terms of GDP for the first time in 2018, and the gap between Guangzhou’s GDP and Hong Kong’s GDP was only 114.163 billion yuan. Moreover, after the period of prosperity experienced by Hong Kong, its status as an economic center declined; subsequently, serious industrial hollowing problems occurred [44]. The growth rate of Hong Kong’s GDP was not as good as that of Guangzhou and Shenzhen.

Temporal comparison of GBA evolution

The GBA is one of the most dynamic economic regions and manufacturing centers in the world [45]. However, before 1978, except Guangzhou, the other cities in Guangdong had agriculture as their pillar industry [46], and Shenzhen in particular was a small village that relied on fisheries [47]. At this time, Hong Kong and Macao were under the rule of Britain and Portugal, respectively. They relied on light manufacturing to lead the development of the GBA [48]. There is no doubt that the development gravity center of the GBA at this time is clearly leaning toward Hong Kong and Macao.

After 1978, the central government of China adopted a series of policy reforms. The cities in Guangdong Province developed an export-oriented economy with cheap labor and land resources and undertook an extensive transfer from various industries, including manufacturing in Hong Kong and Macao. At this time, Hong Kong is still the core of the GBA [49]. It is conceivable that at this time, the development gravity center of the GBA is still biased toward Hong Kong, but with the influence of the Mainland's reform and opening-up policy, the regional development gravity center will inevitably move northward.

With China's efforts to expand its opening up and economic reform after joining the WTO at the end of 2001, the cities of Guangdong Province have ushered in a new momentum of development. Dongguan, which is known as "an important information technology R&D center", and Foshan, which aims to become "an advanced manufacturing base", have especially attracted and developed advanced manufacturing industries and achieved tremendous development [50]. During this period, Guangzhou and Shenzhen were also developing rapidly, so it is obvious that the gravity center of regional development shifted northward.

Policy recommendations regarding the development of GBA

To achieve balanced regional socioeconomic development, the individual cities in the GBA megacity region need effective policies. Based on the findings above, we propose several policy suggestions for the individual cities, as follows: (1) while maintaining high-quality development, Guangzhou and Shenzhen should further connect with other cities to promote their common development; they should move from "struggling singly" to "cooperative operations" and help underdeveloped regions address their shortcomings; (2) Hong Kong and Macao should gradually break down the institutional barriers between themselves as special administrative regions and the mainland, making full use of the mainland’s market, capital, talent and technology and strengthening the "one country, two systems" exchange in the context of the GBA; (3) Foshan and Dongguan should maintain their current positive development momentum, further enhance the development potential of their manufacturing industries, and continue to support the development of high-tech industries; (4) by implementing policies, the GBA should encourage the development potential of cities such as Zhaoqing, Jiangmen, Zhongshan, Huizhou and Zhuhai, enhance the construction of infrastructure, accept industrial transfer to developed areas, promote industrial transformation and upgrades, offer more job opportunities, and stabilize the local population’s employment and living conditions in the local area. Additionally, the cities of the GBA should work to increase their floating populations, promote mutual increases in population, economic factors and consumption, and promote the balanced development of the GBA.