# From fragmentation to integration: Evolving community structure of the Asia-Pacific shipping network since 1890

Han Su, Liehui Wang, Sheng Zhang, Debin Du, César Ducruet

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Han Su, Liehui Wang, Sheng Zhang, Debin Du, César Ducruet. From fragmentation to integration: Evolving community structure of the Asia-Pacific shipping network since 1890. Journal of Transport Geography, 2025, 128, pp.104370. 10.1016/j.jtrangeo.2025.104370. halshs-05218271

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# From fragmentation to integration: Evolving community structure of the Asia-Pacific shipping network since 1890

Han Su, Liehui Wang, Sheng Zhang, Debin Du, César Ducruet

*Journal of Transport Geography*, 2025, 128, pp.104370

***Abstract:*** The Asia-Pacific region, with its dominant maritime character, has steadily increased its importance in the global economy and transportation system over time. A global database of inter port vessel movements between 1890 and 2016 serves to map and analyze the changing topology and community structure of this maritime network, based on existing knowledge about locational, political and economic factors at stake. The principal results reveal pronounced fragmentation during the colonial period, owing to dominant external influences, followed by greater integration post-WWII, driven by national policies and the emergence of logistical hub ports. In parallel, the network is resilient as seen with the stable position of key pivotal ports. Based on the analysis of the evolving community structure, a four-stage port community evolution model within the Asia-Pacific shipping network is proposed, encompassing geographic proximity, colonial dependency, domestic and transnational communities.

***Keywords:*** Asia-Pacific shipping network; fragmentation or integration; Community structure; Complex network; Port community evolution model

## 1. Introduction

In global supply chains, the centers of production and consumption are far away from each other, creating a complex network of trade flows (Kosowska-Stamirowska, 2020). Since the 19th century, globalization and advancements in transportation have rapidly transformed ports and shipping networks worldwide. This has led to the emergence of dense areas of maritime connectivity in Western economies and notably in Asia (Braudel, 1979; Lewis and Wigen, 1999). East Asia, in particular, has garnered significant attention (Broeze, 1989) owing to its prominent maritime character and the rise of “global hub port cities” (Lee et al., 2008). Research has even coined the term “Asian Mediterranean” to describe this region (Gipouloux, 2011), with a central backbone termed “East Asian maritime corridor,” stretching from Singapore in the south to Far East Russia in the north (Ducruet et al., 2011).

During colonial era, the Asia-Pacific region's 13 coastal countries or regions were colonized by seven different countries. Post-WWII, the region became vital for both intra-Asian trade and global shipping routes. Presently, Asia-Pacific ports rank among the world's busiest, with nine of the top ten container ports and 45 of the top 100 ports located here. However, understanding the development trajectory of these ports over a century remains unclear. Maritime routes within this corridor have intensified over time, strengthening internal links through processes of delocalization and institutional transformations. These include shifts from colonization to independence, division to
integration, and economic transformations such as China's reforms, the rise of the Four
Asian Tigers, ASEAN integration, and Japan's economic transformation. On
November 15, 2020, the official signing of the Regional Comprehensive Economic
Partnership (RCEP) confirmed existing commercial trends among the 15 contracting
parties, aligning with the composition of the Asia-Pacific region. Agreements such as
ASEAN and RCEP, have progressively increased integration and connectivity in the
region, with implications for maritime transport, including heightened intra-regional
routes (Li et al., 2022; Chang, 2022). In this complex economic and historical context,
the trend of either fragmentation or integration among port communities in the region
requires further investigation. Despite numerous analyses focusing on East Asian ports,
few have addressed such a broad temporal scope and transnational perspective across
the entire system.

Numerous studies have examined maritime networks' connectivity and geospatial
structure. In particular, identifying community structures in networks isolates tightly
connected groups of nodes, revealing mutual affinities and barrier effects (Ducruet,
2020). Global shipping networks demonstrate a community structure (Sun, 2012),
prominent features of complex networks (Newman, 2004), and influence their
organization of functional and structural core (Xu et al., 2020). These networks are
divided into groups of nodes with dense internal connections and sparse connections
between them (Zheng et al., 2018). East Asia and Southeast Asia are often treated as a
single community (Bai et al., 2023) of global scale research, or the Malacca Strait serves
as a boundary, dividing them into two communities (Pan et al., 2021; Xu et al., 2020).
Consequently, identifying the fragmentation and integration of port communities within
the Asia-Pacific region becomes challenging.

This research particularly investigate the respective role of geographic proximity
and other factors (political, economic, logistical) in the emergence of communities over
time, with the hypothesis that the internal community structure of Asia-Pacific is, at
least partly, resilient to change. Factors such as physical geography, geographical
proximity, global and regional trade patterns, port hierarchy, and functional
specialization influence port system development (Ducruet and Zaidi, 2012).
Geographical proximity is particularly crucial for port system emergence, while river-
based geography also shapes river port systems (Veenstra and Notteboom, 2011).
Institutional factors, national policies, industrial agglomeration, market supply and
demand changes, and technological advancements further drive port system structural
changes (Yang et al., 2017). By observing proximity effects within East Asian
communities, this research aims to gain insights into port and shipping dynamics, as
well as broader territorial and economic influences. Despite the obvious and crucial
importance of maritime logistics to the world economy, only a few works provide a
detailed overview of the long-term evolution and the rules which govern it (Tavasszy,
2011; Kosowska-Stamirowska, 2020). With the global rise of transshipment hub ports,
a comprehensive examination of port system evolution is imperative (Vallega, 1986;
Notteboom, 2010). Understanding shipping model enhances our comprehension of
underlying mechanisms, which in turn can inform more effective decision-making in
maritime logistics and port operations.
Although the related study proposes performing structured empirical analysis on the overall global hierarchy of maritime clusters based on several theoretically grounded propositions, it prioritizes conceptual analysis due to the limitation of data available (Shi et al., 2021). The only known way to map and analyze the long-term evolution of global maritime networks is to extract vessel movement information from the Lloyd's List archives (Ducruet et al., 2018). Utilizing *Lloyd's List* data from 1890s on global shipping interactions, the study employs the community detection method to classify ports according to their role in shaping these patterns. The variations and uneven participation in such structures are verified according to existing knowledge about the region's historical evolution and internal discrepancies within the region. Our goal is to detect the evolution of the port community in the Asia-Pacific shipping network, whether political and economic transformations may have changed the network structure, and how. In addition, based on the integration of multiple complexed influencing factors, an attempt is made to propose an evolutionary model based on the formation and transformation of communities over time.

This study tests the hypothesis that the recently identified hub-feeder structure of East Asia (see Robinson, 1998) is not fully new, but rather is derived from more ancient patterns of maritime circulation in the region. Another hypothesis is that Asia-Pacific had undergone a process of regionalization, characterized by the growing fusion of communities with others. However, as illustrated by the case of North Africa, the multiplication of shipping linkages among Maghreb ports (Mohammed-Chérif and Ducruet, 2016) may not always signify regional integration but rather, a growing dependence upon a fast-growing hub such as Tangier-Med.

The remainder of this paper is organized as follows: Section 2 reviews the literature on maritime flows, particularly in the Asia-Pacific shipping network and the application of existing complex network methods. Section 3 outlines the methodology, covering partition algorithms used for community detection and shipping data. Section 4 examines the port community in Asia-Pacific shipping network, exploring both fragmentation and integration from the 1890s, with an in-depth study of the evolution of major communities. Section 5 proposes a four-stage model of port community evolution, discussing various influencing factors. Lastly, Section 6 summarizes the main findings, outlines the study's contributions, and suggests directions for future research.

## 2. Literature review

### 2.1. *Ports and shipping networks in the Asia-Pacific region*

Global-scale analyses demonstrated the increasing significance of East Asian ports in contemporary container shipping networks after decades of rapid growth (Wang and Wang, 2011; Notteboom, 2006; Lam and Yap, 2011; Li et al., 2015). Together with North America and Western Europe, East Asian ports form a vital core along the main trunk lines or “East-West corridor” (Frémont, 2007; Xu et al., 2015; Liu et al., 2018; Tran and Haasis, 2014; Pais Montes et al., 2012). This contrasts with the late 19th-
century hierarchy of port cities (Ducruet et al., 2018), when most East Asian nodes were
under Western dominance or functioned as relatively isolated subnetworks within
prevailing colonial linkages. This partially explains the recent focus on East Asia as a
single network in studies owing to its intense maritime trade (Calatayud et al., 2017;
Freire Seoane et al., 2013).

Analyses of the global maritime network unraveled the consistency of the East
Asian maritime region based on its internal connectivity. Network analyses, for instance,
was used to delineate a coherent Asian region within global maritime interactions
(Kaluza et al., 2010; Pan et al., 2019). Other analyses have explored the internal
connectivity of the East Asian shipping network (Robinson, 1998; Ducruet et al., 2011),
drawing comparisons with other transshipment basins (Mareï and Ducruet, 2015). A
key finding was that, unlike the Caribbean and Mediterranean networks, the East Asian
network demonstrated a stronger integration of intraregional and interregional traffic
flowing through significant nodes, notably owing to its dominant maritime character.
East Asia exhibits typical characteristics, with intra-regional traffic comprising a
substantial share and increasingly connecting with extra-regional traffic via the same
links and ports (Mareï and Ducruet, 2015).

Despite valuable insights from previous studies, cross-regional analyses regarding port evolution patterns in East and Southeast Asian ports remain limited, with most studies focused on relatively small regions and current circumstances. Examples include port clusters in Chinese coastal provinces (Zhang et al., 2021), the Pearl River Delta container port (Liu et al., 2013), ports in the Yangtze River basin and Yangtze River Delta (Veenstra and Notteboom, 2011; Yang et al., 2017, Jiang et al., 2022), as well as port systems in Japan and Korea (Le et al., 2009), and container port systems in Southeast Asia (Nguyen et al., 2020). The aforementioned works have contributed significant references and empirical analysis to enhance our understanding of ports and shipping networks in the Asia-Pacific region. However, shipping networks remain inherently complex due to the interplay of various factors and actors (Xu et al., 2024), and there remains an urgent need to explore the entire Asia-Pacific networks from a broader spatiotemporal perspective. Wilmsmeier et al. (2014) have demonstrated the necessity and feasibility of expanding geographical scales for comparative studies across different port scales. Yet, the absence of precise data on inter-port relationships has hindered the application of broader network theories to maritime systems, which are often studied through case-specific approaches (Ducruet and Notteboom, 2012). In this paper, the gap is filled with accurate data on unique inter-port relationships from the 1890s.

Furthermore, in terms of the temporal dimension, maritime transport played an
indispensable role in empire-building, including the later stages of colonialism in the
late 19th and early 20th centuries. However, the evolution of the Asia-Pacific port
system under colonial and other external influences during this period remains
underexplored. In addition to the internal driving force of the port, the external driving
force must also be considered. Therefore, extend the research period to the pre-colonial
period is essential to supplement and contribute to the existing literature. This historical
perspective, combined with the analysis of international trade and the emerging global
trade system, holds significant practical implications for the Asia-Pacific shipping network.

Moreover, most studies on port systems have focused on their development in terms of centralization or decentralization (Bird, 1963; Hayuth, 1981; Taaffe, 1963; Notteboom, 2005; Slack, 1990; Wilmsmeier and Monios, 2013), with limited attention given to the fragmentation or integration patterns among ports. However, a transitory process has taken place where old theoretical models started to become obsolete while port geography research began to move away from geography to transport and other disciplines (Ng and Ducruet, 2014). The centralization or decentralization of ports largely depends on the attributes assigned by their connected ports within the maritime network, serving as a key prerequisite for understanding these patterns. By analyzing port communities over the past century, this study traces the evolution of these associated ports and propose a model for fragmentation or integration. This contributes to the theoretical advancement of port and shipping system studies.

## 2.2 Complex networks and community structure identification

The growing field of network science has developed a variety of tools and techniques for understanding the structure and behavior of systems based on their connectivity (Alderson et al., 2020). The significance of topology in maritime transport has prompted many studies to employ complex network structures and related dynamic methods. Since its inception (Robinson, 1968), shipping network analysis has proven to be an effective tool for exploring maritime transportation (Álvarez et al., 2021). A network can be examined in terms of its structure, topology, and characteristics as well as the connectivity with different measures (Kanrak, 2019), including multi-layer modelling approach (Peng, 2023; Xu, 2024).

Community detection has garnered increasing attention in the field of maritime transport studies, since the pioneering study of Kaluza et al (2010). Community structures represent groups of highly interconnected ports, serving as complex network measures (Tagawa et al., 2022). Within a community, numerous connections exist between hub ports and their feeder ports, whereas inter community connections are sparse (Zheng et al., 2018). Different clustering algorithms have been employed in previous studies, including modularity, topological decomposition, the Louvain algorithm, bisecting k-means, blockmodeling, and eigenvalue decomposition. Single Linkage Analysis (SLA) has also been applied to reveal the main hubs of maritime networks, and their respective “nodal regions” (Ducruet et al., 2010b; Wang and Wang, 2011; Ducruet and Notteboom, 2012; Ducruet, 2013; Ducruet, 2017). In this study, it is believed that the search for community structures over a longtime span can shed new light on current patterns, using state-of-the-art methods of network partitioning (Leicht and Newman, 2008; Zheng et al., 2018).

In the last decade or so, clustering methods or “network partitioning” techniques have been applied to a variety of shipping networks at multiple spatial scales, including the global level (Sun et al., 2012; Ducruet and Zaidi, 2012; Pan et al., 2019). However, in global-scale analyses of shipping networks, East Asia and Southeast Asia are often treated as a single community (Bai et al., 2023), or the Malacca Strait serves as a
boundary, dividing them into two communities (Pan et al., 2020; Xu et al., 2020). This approach overlooks the internal dynamics of fragmentation and integration within the East Asian shipping network and fails to capture their evolutionary process. Therefore, a more granular analysis is necessary to downscale from global to regional, to explore and analyze the community structures within this geographical unit.

However, existing literature often employs community detection merely as a static analytical tool, when applied in isolation within complex network systems, such usage tends to result in analytically shallow interpretations. This highlights the need for deeper investigation into the evolutionary dynamics of port communities, supported by historical context and explanatory modeling. The increasing availability of historical shipping records allowed for the analysis of past shipping networks with regard to political border change. This is the case of Northwest Africa from colonial to global (Castillo and Ducruet, 2020), South Asia before and after the East Indies British Empire (Tsubota et al., 2017), the changing community structure of the Soviet ego network before and after the collapse (Zreik et al., 2017), and the shrinking connectivity of North Korea's shipping network (Ducruet et al., 2017). Additionally, it was found that certain small and medium-sized European ports form clusters or communities with former colonial counterparts, such as France/Antilles/West and North Africa, Portugal/Brazil/Angola, Spain/Latin America. By contrast, relatively few studies have explored these dynamics in East Asia, which are not aligned with the region's unique and complex historical and economic background.

# 3. Data and methodology

## 3.1. *Research area*

The Asia-Pacific maritime corridor typically spans from Russia Far East in the north to Singapore and Malaysia in the south (Rodrigue, 1996). From a geographical point of view, this region is also known as the Mediterranean Asia (Gipouloux, 2011), including the South China Sea, Sea of Japan, East China Sea, Yellow Sea, Sulu Sea, and Celebes Sea (Fig. 1). Notteboom (2022) denotes this area as the Asia-Pacific region. However, despite the maritime unity characterizing East Asia and its hinterlands (Lee et al., 2008), it is essential to recognize the region's wide diversity in political and economic systems throughout history. In the 19th and mid-20th centuries, the Asia-Pacific comprised one industrialized country (Japan), several kingdoms, and colonial outposts of Western powers, aiming for further dominance. This landscape underwent significant reorganization after WWII, marked by the downfall of the British Indian Empire, China's transformation from the Qing dynasty to socialist rule, the partitioning of Korea, and the Cold War.
<figure><img src="image_2.png" /><figcaption>**Fig. 1.** Asia-Pacific maritime corridor.</figcaption></figure>

This study covers the research period from 1890 to 2016. During this timeframe, 16 countries, including China, Japan, South Korea, and several Southeast Asia nations, participated in the shipping network; however, only a few hub ports were connected across the regions. Fig. 2 illustrates the annual changes in the number of ports involved in regional connectivity and the number of countries participating in the Asia-Pacific shipping network.

<figure><img src="image_3.png" /><figcaption>**Fig. 2.** Evolution of the number of ports in the Asia-Pacific shipping network, 1890-2016.</figcaption></figure>

## 3.2. Data

This study utilizes *Lloyd's List* archives, a unique and highly representative source providing daily inter-port connectivity data since 1880, with limited references and applications in existing literature (Ducruet et al., 2018). In particular, this dataset provides a list of merchant vessels and their latest inter-port movement. The extraction of vessel movements from paper sources worldwide (1890 to 2008) was facilitated by
Optical Character Recognition (OCR) tools, extracting one entire publication every five years and resulting in a database comprising 769,272 vessel movements and approximately 200,000 potential connections among nearly 9,000 ports globally. Subsequently, data for the period 2009 to 2016 were exclusively collected for container ships owing to their concentration of approximately 80% of the world trade value (UNCTAD, 2021). A processed sample of the original dataset is presented in Table 1, organized into connections between ports of origin and destination, including the number of routes connecting these pairs. From 1890 to 2016, the global port connections sampled at ten-year intervals totaled 243,874, with 492,837 routes (total vessel movements). In the Asia-Pacific shipping network, intra-regional port connections totaled 31,957, with 133,465 routes.

<table><caption>Table 1 Asia-Pacific shipping data extracted from Lloyd's List</caption><thead><tr><th>No.</th><th>Source port</th><th>Target port</th><th>Weight</th><th>Year</th><th>Category</th></tr></thead><tbody><tr><td>1</td><td>Anyer</td><td>Jakarta</td><td>2</td><td>1890</td><td>all vessel</td></tr><tr><td>2</td><td>Aomori</td><td>Haiphong</td><td>1</td><td>1890</td><td>all vessel</td></tr><tr><td>......</td><td>......</td><td>......</td><td>......</td><td>......</td><td>......</td></tr><tr><td>1844</td><td>Aomori</td><td>Miri</td><td>1</td><td>1950</td><td>all vessel</td></tr><tr><td>1845</td><td>Aomori</td><td>Yokohama</td><td>2</td><td>1950</td><td>all vessel</td></tr><tr><td>......</td><td>......</td><td>......</td><td>......</td><td>......</td><td>......</td></tr><tr><td>10246</td><td>Akita</td><td>Busan</td><td>1</td><td>2008</td><td>all vessel</td></tr><tr><td>10247</td><td>Akita</td><td>Sakata</td><td>2</td><td>2008</td><td>all vessel</td></tr><tr><td>......</td><td>......</td><td>......</td><td>......</td><td>......</td><td>......</td></tr><tr><td>31956</td><td>Shanghai</td><td>Liuheng</td><td>1</td><td>2016</td><td>container</td></tr><tr><td>31957</td><td>Shanghai</td><td>Lianyungang</td><td>2</td><td>2016</td><td>container</td></tr><tr><td colspan="6">Total</td></tr><tr><td>31957</td><td>480 (unique)</td><td>507 (unique)</td><td>133465</td><td>31 (years)</td><td>all vessel/container</td></tr></tbody></table>

Based on Lloyd's data, the global traffic share of the Asia-Pacific route is calculated (Fig. 3), representing the proportion of ship movements involved in Asia-Pacific ports compared to the total global routes. As a preliminary result, the global traffic share of the Asia-Pacific region skyrocketed from 4% in 1890 to over 28% in 2008. Similarly, the intra-Asia-Pacific's share of global and Asia-Pacific routes increased from 2% and 38% to 21% and 74%, respectively. This trend can be divided into three phases: from 1890 to the end of WWII, with slow growth or even a decrease in share; from the end of WWII to 1970, witnessing a slight increase; and from 1970 onwards, marked by a rapid rise in both the share of Asia-Pacific routes globally and the share of intra-Asia-Pacific routes within the Asia-Pacific region. Overall, these findings underscore the growing significance of Asia-Pacific ports and shipping networks within the global maritime transportation network as well as its growing internal connectivity.
<figure><img src="image_4.png" /><figcaption>Fig. 3. Share of vessel calls in Asia-Pacific shipping network, 1890-2008.</figcaption></figure>

### 3.3. Methodology

#### 3.3.1. Complex networks and degree centrality

Node degree is a widely used metric in complex network analysis (Wang et al., 2016), which quantifies the significance of nodes, with degree $D_i$ defined as the number of connections between node i and other nodes. In the context of shipping networks, higher degree values signify greater connectivity and influence in the network.

The node degree is calculated as:

$$D_i = \sum_{j=1, j \neq i}^{n} L_{ij}$$

where $L_{ij}$ denotes the number of edges between ports i and j, and n represents the total number of port nodes.

While node degree reflects port connections, weighted node degree gauges the strength of these connections within the weighted shipping network, strength being measured by the number of calls. Port node strength, or weighted degree, is the sum of weighted connections to all other port nodes in the network:

$$S_i = \sum_{j \in N_i} W_{ij}$$

Here, $S_i$ represents the weighted degree of port i, $N_i$ denotes the set of ports i, and $W_{ij}$ denotes the weight of routes between port i and others in the network.

At the macro level, the two indices are used to assess overall network growth and density over time, helping to characterize broader structural shifts in regional connectivity. At the micro level, they identify hub or dominant ports within the network, and trace the evolution of key nodes across different historical stages. As such, they serve as a consistent foundation for subsequent analyses in Sections 4.1 and 4.2.

#### 3.3.2. Identification of the community structure

Community structure is characterized by an aggregation mode and a functional structure within a network (Wang and Jing, 2017). In this study, port communities were identified based on clustering and assessing the strength of connections between ports,
with geographical significance revealing port agglomerations in the shipping network. Notably, community structures include both network hub nodes and surrounding small nodes. A community comprises highly interconnected nodes, with nodes within a community having numerous internal connections and few external ones (Tagawa et al., 2022).

To identify community structure, modularity-based approach is employed. Under the modularity maximization method, network partitions are assigned disjoint modules based on core Q values (Newman and Girvan, 2004), which govern community division. Louvain algorithm, used in this study, is an effective community detection method and provides high-quality and accurate community partitions. The formula for calculating ΔQ is as follows (Blondel, 2008):

$$ \Delta Q = \left[ \frac{\sum in + 2k_{i,in}}{2m} - \left( \frac{\sum tot + k_i}{2m} \right)^2 \right] - \left[ \frac{\sum in}{2m} - \left( \frac{\sum tot}{2m} \right)^2 - \left( \frac{k_i}{2m} \right)^2 \right] $$

where m denotes the sum of the strengths of all port connect pairs in the network; Σ in and Σ tot represent the sum of internal port connection strengths within the module and the sum of the port strengths, respectively; and k_{i,in} indicates the sum of connection strengths between the port and other ports within the module (or community).

The Louvain algorithm operates in two phases. Initially, it seeks a local maximum of modularity, indicating optimal communication division. Consequently, it builds a new network using identified communities. This process iterates until no further changes occur, maximizing modularity (Blondel, 2008). Modularity Q, ranging from 0 to 1, reflects the accuracy of community division. Values between 0.3 and 0.7 typically indicate significant results, meaning that the detected community structure is meaningful within the network.

The Louvain algorithm is selected in this study for its high computational efficiency, scalability, and suitability for large, weighted, and undirected networks. Compared to alternative methods such as spectral clustering, bisecting k-means, blockmodeling, and eigenvector decomposition, Louvain does not require a predefined number of communities and excels at uncovering modular and hierarchical structures. These advantages are particularly relevant given the characteristics of the dataset, which spans from 1890 to 2016 and exhibits substantial variation in both network scale and edge weights. Its modularity optimization mechanism allows for robust detection of tightly connected port clusters and evolving regional integration or fragmentation patterns. Therefore, the Louvain algorithm provides a consistent and powerful framework for identifying and comparing dynamic community structures in the Asia-Pacific shipping network over time.

### 3.3.3 Variables and empirical models

To analyze the influencing mechanism of port fragmentation or integration, the regression model is calculated to provide empirical support. The explanatory variables are categorized into three dimensions: geographic proximity, political proximity and economic proximity. First, geographic proximity is measured using the distance of maritime transportation between ports, and then the reciprocal of the distance is used
as a variable. Second, political factors such as colonial ties, national independence and cross-national regions influence whether port fragmentation or integration at different stages. Therefore, this paper uses whether there is a colonial relationship (colony to suzerainty link) and whether there is a common suzerainty (colony to colony link) to characterize the colonial link, which is 1 if yes, and 0 if no. In addition, it considers whether it is in the same country or in the same region, which is 1 if it is yes and 0 if it is no. These are dummy variables. Third, economic proximity is analyzed in terms of bilateral economic and trade relations, as measured by the signing of trade agreements or not (0,1), the volume of bilateral trade, and the gap in GDP. Data are from the CEPII database, covering the period is 1950-2016. The dependent variable is whether the port pair is in the same community (1890-2016), 1 if yes, 0 otherwise. Given the binary nature of the dependent variable, a logistic regression model is applied.

# 4. Evolution pattern and characteristics of the community structure in the Asia-Pacific shipping network

## 4.1 Evolution characteristics of the Asia-Pacific shipping network

For a better understanding of port communities from the perspective of fragmentation or integration, it is essential to examine the structure and spatial features in the Asia-Pacific shipping network. Based on the cartography of the Asia-Pacific shipping network, several trends characterize the evolution of the port system in the Asia-Pacific region from 1890 to 2016. These findings are listed below with detailed descriptions, including the number of ports and connections, and shipping network patterns.

(1) Rapid growth in Asia-Pacific shipping network, whereas the reduction in the number of port communities to four.

Between 1890 and 2016, the Asia-Pacific region witnessed a substantial expansion in both the number of ports and the scope of maritime connections. Notably, the growth rate differed significantly between the colonial and post-WWII periods, with a pronounced acceleration observed after WWII. There has been a considerable surge in shipping traffic post-WWII, indicated by a slope rise from 9.75 (1890–1940) to 45.95 (1950–2000). The post-war era witnessed Asia-Pacific countries gradually gaining independence, leading to rapid port development fueled by a complex interplay of political, economic, and logistical factors. Consequently, the number of ports and route connections increased significantly, rising from 101 in the 1950s to 328 in the 2000s, and from 857 to 5186, respectively, marking increases of 3.2 and 6.1 times (Fig. 4).
<figure><img src="image_5.png" /><figcaption>**Fig. 4.** Evolutionary characteristics of ports and route calls, 1890–2016.</figcaption></figure>

Note: S1, S2 and S3 represent the slopes of the three stages respectively.

Similarly, the analysis of complex network indicators reveals a gradual increase in the average node degree and weighted degree of the Asia-Pacific region, with a notable increase observed after the 21st century, underscoring the region's strengthening of its position within the network (Fig. 5).

<figure><img src="image_6.png" /><figcaption>**Fig. 5.** Evolutionary characteristics of community and degree, 1890-2016.</figcaption></figure>

During the colonial period, the number of communities remained relatively stable, ranging from four to six. Post-WWII, an increase was observed, fluctuating between six to nine. Since the early 21st century, although ports, routes, and node degrees increased substantially, the number of communities declined from nine in 2000 to four in 2016 (Fig. 5). Therefore, while shipping networks in the Asia-Pacific demonstrate rapid growth, the number of communities post-21st century align with colonial-period levels, indicating an overarching trend toward community integration.

(2) Shipping network patterns anchored by pivotal key port nodes.

In the 1890s, the distributions of shipping links were relatively dispersed. By the 1900s, three poles emerged: Singapore, Hong Kong, and Yokohama, forming a triangular pattern. In the 1940s, Yokohama and Kobe constituted the northern bipolar system, while Hong Kong and Shanghai formed the central bipolar one, with Singapore
as the southern independent pole. By 1960, three-quarters of the top 15 shipping links were domestic routes in Japan, with the remainder held by Singapore, Hong Kong, Yokohama-Kobe. In 1980, intra-regional linkages dominated, obscuring cross-regional patterns. By the 2000s, Yokohama and Kobe receded to the second tier, while Busan emerged. Since 2012, a chain pattern of Singapore, Hong Kong, Shanghai, and Busan has emerged (Fig. 6), with the strongest links spanning across the region. The top 15 links have changed, with half of them being domestic routes in China, whereas a quarter are dominated by Singapore, Hong Kong-Shanghai, and Busan.

Therefore, over the past 130 years, the Asia-Pacific shipping network has evolved from a triangular pattern of Singapore-Hong Kong-Yokohama to a chain pattern of Singapore-Hong Kong-Shanghai-Busan. Notably, these structural shifts are closely tied to the evolving centrality of key hub ports within the network. In a manner consistent with the “rich get richer” principle (Alderson et al., 2020), these ports experienced accelerated growth, developed into global “megaports” and are today essential in global logistics.

<figure><img src="image_7.png" /></figure>

<figure><img src="image_8.png" /></figure>

<figure><img src="image_9.png" /></figure>

<figure><img src="image_10.png" /></figure>

<figure><img src="image_11.png" /></figure>

<figure><img src="image_12.png" /></figure>

<figure><img src="image_13.png" /></figure>

<figure><img src="image_14.png" /></figure>

<figure><img src="image_15.png" /></figure>
<caption>**Fig. 6.** Evolution of Asia-Pacific shipping network pattern, 1890-2016.</caption>

*Notes*: Solid black circles indicate the period when the port first appeared or reappeared in the top tier, and dashed black circles indicate the period when the port disappeared from the top tier.

## 4.2 Evolution process of port communities in the Asia-Pacific shipping network

Fig. 7 illustrates the structure of port communities from 1890 to 2016. Before WWII, community sizes - as measured by the number of ports per community- were relatively uniform. However, after WWII, the Japanese and Singaporean communities expanded, followed by the Chinese community in the 21st century. In the sub-community structure of the Asia-Pacific shipping network, the hierarchical gap widened over time, indicating an increasing trend toward polarization. By 2016, the four major communities accommodated 27, 85, 95, and 64 ports, respectively. The Chinese community exhibited a clear core-periphery structure with widening gap of port weighted degree and links. Conversely, existing studies have shown that the port system in Southeast Asia has become more competitive and less concentrated (Nguyen et al., 2020). This is consistent with the structural patterns shown in Figure 7, where the concentration of Southeast Asian ports has gradually declined over time. Meanwhile, in the Northeast Asian community, dominated by either Busan or Yokohama, the intra-community hierarchical gap narrowed.

Regarding dominant ports within and between communities, nodes within communities are predominantly linked to main hub nodes, reflecting the dominance of hub nodes in the shipping network structure. This is particularly notable in the case of the Hong Kong community of 1890, where nearly all intra-community links converge on Hong Kong (Fig. 7a). Similarly, inter-community connections are dominated by major ports, known as bridge ports, crucial for community connection and integration. The evolution of bridge ports and network hierarchies has been strongly influenced by economic and geopolitical shifts. After 1980, gateway ports such as Yokohama and Kobe began to decline (Fig. 7e), and in the 21st century there was a shift to Shenzhen and Shanghai, and Chinese ports increasingly serving as bridges between communities (Fig. 7f). Meanwhile, transshipment ports like Singapore and Hong Kong have been resilient to change.
<figure><img src="image_16.png" /><figcaption>**Fig. 7.** Port community structure in the Asia-Pacific shipping network (1890-2016)</figcaption></figure>

Influenced by various factors such as the rise and fall of key hub ports, geographic proximity, political economy, and technological advancements, ports communities in the Asia-Pacific region have evolved from fragmentation during the colonial period to
integration, forming four major communities. The following section provides a more
detailed account of the formation and consolidation of these port communities.

(1) Hong Kong and Shanghai were integrated into the same community, while ports in northern China formed separate communities.

In the late 19th and early 20th centuries, Chinese ports were divided into three
communities, constituting 55% of the total ports in the Asia-Pacific region (Fig. 8,
1890). These communities were centered upon Shanghai, Hong Kong, and Xiamen,
namely the port with the highest node degree within each community. The Shanghai
community included ports along the Yangtze River, southeast coastal ports, northern
ports, and Japanese ports such as Nagasaki, totaling eight ports. The Xiamen
community comprised ports along the west coast of the Taiwan Strait and those with
close ties to Taiwan, totaling six ports, including Fuzhou, Tainan, Tamsui, Yingkou, and
Kaohsiung. The Hong Kong community encompassed Chinese ports such as
Guangzhou / Huangpu and Haikou, along with Southeast Asian ports in Vietnam,
Malaysia, and Indonesia, totaling 12 ports. Geographic proximity appears as a strong
influential factor to explain the distribution of communities.

From 1890 to 1940, the status of ports in Hong Kong and Shanghai gradually improved, and the scope of the community gradually expanded. The weighted degree of Hong Kong increased from 106 to 182, and that of Shanghai increased from 52 to 176, ranking second and third, respectively, in the region. Most goods imported from Europe and America were concentrated in Hong Kong and Shanghai, respectively. As seen in Table.2, Hong Kong played a pivotal role in the transfer of foreign goods to ports such as Fuzhou, Shantou, Xiamen, Guangzhou, and Taiwan, whereas goods concentrated in Shanghai were transported to the Yangtze River Basin and North China. From the perspective of the Hong Kong community, in the early 20th century, due to the expansion of China's domestic ports, the Qing government leased New Territories to Britain, and Hong Kong carried more transit trade from mainland China, strengthening its ties with China's coastal ports, and moving northward. On the other hand, from the perspective of the Shanghai community, from the "Nanjing Treaty" of "Five Ports of Commerce" to the beginning of the 20th century, colonial nations completely controlled the rights of ports, or "unequal treaty" based on the forced opening of the "treaty ports" between about 1840 to 1950. It is largely an "enclave economy", and 71% of the docks in Shanghai are foreign at that period. It established a huge shipping network with Shanghai as the center, opened many international and domestic routes, and expanded the scope of the Shanghai community (Jin, 1982).

With the expansion of the two communities centered on Shanghai and Hong Kong
in the 1920s, Shanghai and Hong Kong merged into the same community (Fig. 8, 1920).
In 1910, 1920, and 1930, the largest number of routes in the Asia-Pacific region was
between Kobe and Yokohama. However, in 1940, the number of routes between the
Shanghai and Hong Kong ports was 56, which was the largest. In 1940, the number of
ports within the Shanghai-Hong Kong community was as high as 19, of which 63%
were Chinese ports and 31% were Indo-China Peninsula and Incheon ports. As the
functions of Chinese ports gradually improved, the scope of the shipping networks of
Hong Kong and Shanghai gradually expanded, and Chinese ports formed a long-term
trade circle with Hong Kong and Shanghai as the core (Fig. 8, after 1920).

In 1984, China began reforming its port management system, allowing it to gain local autonomy and increase its shipping vitality (Zhang, 2015). The number of Chinese ports increased suddenly since the 1990s. From 12 in 1950-1980, it increased to 26 in 1990, and then to 43 in 2000. Port centrality also gradually increased, with the average degree increasing from 6.7 in 1950 to 11.1 in 1970 and 12.6 in 1990. Simultaneously, the number of ports contained within the community gradually increased, and a tight domestic port community was formed (Fig. 8, 1960-1980).

Since the beginning of the 21st century, the number of ports in China has been increasing, and international hub ports have emerged. In 2016, the number of ports in China reached 68, accounting for 1/4 of the total ports in the Asia-Pacific shipping network. In addition, 5 of the top 10 ports regarding degree and 10 of the top 20 ports are Chinese. Shanghai, Hong Kong, Shenzhen, and Beilun (part of Ningbo Zhoushan port) are gradually becoming international hub ports and forming a port community in southern China centered on the above ports. These ports are closely connected, have a high degree of network agglomeration, and include some ports in Southeast Asia, with 47 ports in the community (Fig. 8, 2008). In the early 21st century, northern Chinese ports formed a community with northeast Asian ports such as Korea and Japan. However, with the development of hub ports in northern China, such as Qingdao, Qianwan, and Dalia, their international hub status has increased, and their dependence on Busan has decreased, gradually eliminating the dominant position of Korean ports. Since 2016, an independent northern Chinese port community has emerged, containing 29 ports, 76% of which are Chinese (Fig. 8, 2016).

<table><caption>Table 2 Share of foreign goods imported through Hong Kong, 1869-1904 (%)</caption><thead><tr><th>Year</th><th>Guangzhou</th><th>Shantou</th><th>Qiongzhou</th><th>Beihai</th><th>Fuzhou</th><th>Xiamen</th><th>Taipei</th><th>Gaoxiong</th><th>Ningbo</th><th>Wenzhou</th><th>Yingkou</th><th>Yantai</th><th>Tianjin</th></tr></thead><tbody><tr><td>1869</td><td>99</td><td>92</td><td>-</td><td>-</td><td>92</td><td>73</td><td>-</td><td>16</td><td>3</td><td>-</td><td>9</td><td>9</td><td>3</td></tr><tr><td>1874</td><td>99</td><td>99</td><td>-</td><td>-</td><td>84</td><td>88</td><td>-</td><td>53</td><td>31</td><td>-</td><td>16</td><td>8</td><td>6</td></tr><tr><td>1885</td><td>99</td><td>92</td><td>99</td><td>99</td><td>69</td><td>86</td><td>73</td><td>69</td><td>1</td><td>0</td><td>9</td><td>10</td><td>8</td></tr><tr><td>1896</td><td>99</td><td>95</td><td>84</td><td>100</td><td>79</td><td>77</td><td>76*</td><td>87*</td><td>2</td><td>5</td><td>20</td><td>21</td><td>8</td></tr><tr><td>1904</td><td>98</td><td>92</td><td>97</td><td>97</td><td>75</td><td>62</td><td>-</td><td>-</td><td>21</td><td>0</td><td>14</td><td>14</td><td>7</td></tr></tbody></table>

Notes: * data for 1894. Source: Historical materials of old customs of China.

(2) Northeast Asian port communities have shifted from national boundaries to regionalization.

During the colonial period, with the development of Japanese ports, the number of ports accommodated by the community gradually increased, establishing it as the dominant port communities in Northeast Asia. At the end of the 19th century, the Japanese port-centered community had close ties with ports in the Philippines (Fig. 8, 1890). The Japanese ports of Yokohama, Kobe, Aomori, and Hakodate belonged to the same community as the Philippine ports of Manila and Iloilo. During the colonial era, the scope of the Japanese port community expanded, and Japanese ports formed close
associations with ports on the Korean Peninsula, North China, through colonization and the lease of Chinese land. Among these, Qingdao (occupied in 1914), Taiwan (occupied in 1895), Busan, and Incheon (occupied in 1910) formed a community with Japanese ports. In addition, Japanese and Northeast Chinese ports were in the same community for five of the seven time periods from 1890-1950. During WWII, due to the close geographical distance between the northeastern ports of China and the Japanese port and Japan's support of the pro-Japanese regime (Manchuria State, March 1932-August 1945), Japan was able to incorporate the port of Northeast China into the Japanese port community. Treaties were also signed between Japan and numerous overseas ports within the Asia-Pacific region, such as Korea, which was occupied in 1910 and remained occupied up to the end of WWII, for rice imports, among other trades.

After WWII, countries in Northeast Asia adopted different paths of trade and economic development, resulting in a long-term division of port communities within national boundaries. In the 1950s-1970s, the ports of the Korean Peninsula were still in the same community as the Chinese or Japanese ports; however, after the 1970s, the number of Korean ports increased and formed a domestic port community. Thus, from the 1970s to the end of the 20th century, the Chinese, Korean, and Japanese ports formed three differentiated communities. In the 1980s, the three communities were centered in Hong Kong, Busan, and Yokohama, containing 32, 17, and 91 ports, respectively (Fig. 8, 1980).

In the 21st century, the characteristics of Northeast Asian port communities are similar to those of the colonial era. The ports of northern China are integrated into a trade circle dominated by Japan and Korea, forming a community that includes the ports of China's Bohai Sea, the Korean Peninsula, and the ports of Japan's west coast. However, dominant ports emerged according to different causes in the two periods. Unlike the colonial era, when Japanese ports were the core, Busan was the absolute core hub. The degree of Busan port increased from 78 in 2008 to 199 in 2016, surpassing Hong Kong (143), Shanghai (140), and Singapore (133) and ranking first in the Asia-Pacific shipping network. In 2013, the number of ports in the Busan-centered port community reached 85, including Chinese ports such as Shanghai, Qianwan, Dalian, and Qingdao; Japanese ports; and Russian ports. During the colonial period, this was partly due to the Japanese colonization of northeastern China and the Korean Peninsula. However, in the 21st century, this was due to economic and trade links, as well as liner shipping strategies under marketization. Additionally, Kobe port functions suffered from fierce competition in the early 1990s as well as from earthquake in 1995, having provoked the shift of large container traffic volumes to Busan in South Korea. The strengthened economies of transport density allowed Busan to expand its hinterland to regions whose container shipping operations had not even been directly affected by the earthquake, such as eastern Japan (Xu et al., 2018).

(3) Southeast Asian ports from fragmentation to integration.

During the colonial period, eight coastal countries in Southeast Asia were colonized by different colonizers—Britain, France, the Netherlands, and Spain—who constructed trade networks that suited their interests. During this period, the shipping links between the Indo-China Peninsula and maritime island countries, such as
Indonesia, were relatively fragmented and split into four communities for a long time with limited internal stability. The four communities formed were Singapore community, Jakarta community, Manila community, and ports in the Indo-China Peninsula such as Ho Chi Minh, which formed the same community as Hong Kong.

Specifically, ports on the Indo-Chinese Peninsula were in the same community as ports in southern China, such as Hong Kong, due to strong shipping connectivity. In 1890 and 1900, the number of route connections between Hong Kong and Ho Chi Minh City was 30 and 20, respectively, ranking first in the Asia-Pacific shipping network. Therefore, Ho Chi Minh City, Da Nang, Haiphong, and other Vietnamese ports remained part of the Hong Kong community throughout the 1890s to 1940s (Fig. 8). However, the Malay Peninsula, Indonesia, and the Philippines developed their own communities. In the 1890s, the Singapore community contained six ports involving five countries, whereas the Jakarta community contained eight domestic ports. By 1940, the Singapore community consisted of 24 ports involving nine countries; similarly, 88% of the 17 ports in the Jakarta community were domestic. The Philippine port community fluctuated considerably, forming the same community as Japanese ports in the 1890s, with Chinese ports from the 1920s, and Singapore ports from the 1940s.

Regarding the stability of Southeast Asian port communities, the Indo-China Peninsula community and the Philippine ports showed limited stability during the colonial period. This is because there were few fixed routes and shipping volumes between the ports. Shipping connections were sparse, and the tightness within the community was not strong. However, the Indonesian community in Jakarta was relatively more stable and remained largely independent. The Jakarta-centered community included all Indonesian ports in 1890, 1900, 1910, and 1930, containing eight, six, four, and seven ports, respectively. Only a few ports, such as Singapore, Malaysia, and Japan, were included in the community in 1920 and 1940. The main reason is that the Netherlands colonized Indonesia for 350 years, starting in the late 16th century, monopolizing Indonesia's foreign trade and forming a tight network of domestic ports within Indonesia, mainly through sea transport. Therefore, during the Dutch colonial period, Indonesia formed a stable and independent community for a long time but was also influenced by its foreign trade policies, briefly forming the same community as the others.

After WWII, Southeast Asian countries gained independent, and to navigate the complexities of great power politics, Southeast Asia chose to pursue regional unity as a means of addressing the evolving international landscape. With ASEAN in 1967 and the gradual removal of trade barriers such as tariffs, port links among Southeast Asian countries became increasingly close under the effects of trade transfer and trade creation. In the 1970s, the Indo-China Peninsula community centered in Singapore and the community centered in Jakarta became integrated with each other (Fig. 8, 1970). In the 1980s, Vietnamese ports gradually separated from Hong Kong and other Chinese coastal ports community and were integrated into the Southeast Asian community (Fig. 8, 1980). With the stabilization of the political map in Southeast Asia and the continued promotion of economic integration measures, such as the ASEAN Free Trade Area, the Singapore-centered Southeast Asian port community has been developing steadily and
continuously, marked by reinforced integration (Fig. 8, 1970-2016).

The number of ports in the Singapore community gradually increased and exhibited a trend of concentration. First, the number of ports increased from 22 in the 1950s to 48 in the 1970s and 104 in the 2000s. Secondly, the concentration trends in the community can be observed in two dimensions. On the one hand, the number of ports integrated into the Singapore community has gradually increased from the ports in Southeast Asia. 36%, 56.8%, and 73.8% of all ports, respectively, were in Southeast Asia and were included in the community in 1950, 1970, and 2000, respectively. On the other hand, from the perspective of the Singapore community, the number of ports in Southeast Asia within the community increased from 81.8% in 1950 to 87.5% in 1970, and then to 89.4% in 2000, showing the concentration of ports in Southeast Asia. Such trends have a lot to do with the overwhelming prominence of Singapore as a major transshipment hub on the Europe-Asia corridor, whose port activity is mainly transshipment to/from Southeast Asian feeder ports. Competition only emerged in the early 2000s with the development of Malaysian ports such as Tanjung Pelepas and Port Klang.
<figure><img src="image_17.png" /><figcaption>**Fig. 8.** Evolution pattern of port community in the Asia-Pacific shipping network (1890-2016).</figcaption></figure>

*Notes*: The circles in 1920, 1970, 2000, and 2016 represent the periods when the Southern China, Southeast Asia, Northern China, and Northeast Asia communities formed, respectively. The circle in 2016 represents the final formation of four major community patterns. Only the top five port communities with the largest number of ports are labeled in the legend.
# 5. Evolutionary model and mechanisms of the community structure in the Asia-Pacific shipping network

## 5.1 Evolutionary model of the community structure in the Asia-Pacific shipping network

Based on the characteristics of port development and community evolution in Asia-Pacific shipping networks spanning 1890 to 2016, a four-phase evolutionary model has been abstracted and summarized: decentralized geographic proximity community (early port development and early colonial period), colony-dependency community (colonial period), nationally bounded community (post-WWII to the end of 20th century), and transnational community (21st century) (Fig. 9).

<figure><img src="image_18.png" /><figcaption>Fig. 9. Port community evolution model.</figcaption></figure>

Port development during the initial period was marked by fragmentation and dispersion, with minimal external connections. Geographical proximity emerged as pivotal in shaping community structure, fostering the formation of small port communities mostly defined by geographical proximity.

During the colonial period, geographical proximity was no longer the single primary factor. Colonial powers formed direct trade links with specific colonized ports, which became central hubs for maritime transport. These colonial ports served as collection and distribution centers, integrating them into the same community as home ports of colonial power and those with close trade links, like for the British and Dutch East Indies empires. Technically, ports of the colonial power functioned as home ports and the colonial ports were hubs or collectors.
During the third phase, spanning from post-WWII to the late 20th century, the evolution of port development and community structure was shaped by national independence and globalization. The ports that developed as a priority emerged as domestic or regional hubs by implementing containerization, expanding maritime routes, and attracting shipping lines. Regarding the community structure, ports broke away from communities dominated by the same colonial power state and transformed into communities with national boundaries to form domestic port communities. This is primarily because the hub ports of each country serve their ports, and the connection system with other ports in the country is far greater than that with other ports in the entire region.

With the development of the modern supply chain system, the development of the port system and community structure has entered the fourth phase of the post-21st century, that is, the transnational community. The boundaries of the community break through national boundaries and are dominated by larger subregions. Meanwhile, when the status of ports gradually strengthens, they become independent from the marginal subordinate status in the original communities, form domestic communities by combining with their ports, and then attract ports from neighboring countries.

## 5.2 Evolutionary mechanisms of the community structure in the Asia Pacific shipping network

By investigating the respective role of geographic proximity and other factors (political, economic, logistical) in the emergence of communities over time, three primary factors shaping community structure can be summarized (Boschma, 2005): geographic proximity, political proximity, and economic proximity, drawing on the concept of multidimensional proximity. Geographic proximity, measured by distances between ports, consistently influences community formation, with proximate ports more likely to belong to the same community, particularly evident during the colonial era. Political proximity, comprising shared suzerainty, independence, or alliance, has shaped the alignment of community structure in different periods. Economic proximity denotes market factors such as economic and trade development, industry shifts, technological advancements, and the driving force of economic and trade organizations.

Geographic proximity prioritizes ports belonging to the same community, whereas non-geographical proximity prioritizes ports that belong to different communities. In the early colonial period, the seven communities in 1890 were geographically proximate and there was no cross-regional community. Geographic proximity and regional integration seem to explain the delineation of most nodal regions (Ducruet and Notteboom, 2012).

The community structure of a network cannot be explained solely based on geographical constraints, and geopolitical considerations must be considered (Guimerà et al., 2005). During the colonial period, owing to close ties, the ports of the colonies became the same community as home ports of colonial power. On the other hand, national colonization causes the port community to break through geographic proximity, and the geographic proximity of the colonial ports also forms community isolation. For example, eight coastal countries in Southeast Asia were colonized by five different
states, which established maritime trade networks in line with their national interests and split into different communities before WWII.

After WWII, countries in the Asia-Pacific region formed independent sovereign states and implemented policies to promote the development of domestic ports. This applies well to the rise of Asian Tigers and the development of China's coastal ports such as Shanghai. Regarding community division or integration, policies implemented by various countries after WWII enabled domestic ports to form close ties and promoted the formation of domestic port communities.

Since the 21st century, the formation of alliance organizations and communities has surpassed the sovereign state of the port community, which has intensified the degree of regionalization. For example, the establishment of ASEAN, from five countries in 1967 to 10+3 countries, and then to the Regional Comprehensive Economic Partnership (RCEP). As in ASEAN, through the gradual elimination of trade barriers, such as tariffs, internal connectivity is increased through trade transfers and trade creation. In contrast, Northeast Asia remained fragmented in the absence of an economic union or an integration policy until South Korean ports, fostered the emergence of a coherent hub region. However, such a community may still be volatile given its reliance on logistical forces.

The economic and trade factors include global industrial shifts, port investment management, technological developments, and liner service strategies, mainly after the independence of the countries. Port authorities, transitioning from first-generation to fourth-generation ports, have evolved into complex entities managing port network communities to provide integrated transportation and logistics services for their hinterlands (Notteboom, 2022). Changes in port management, technological upgrades, and other factors have encouraged them to become core ports in the community and attract more ports to join. Previously, geographic location along with investment were the favorable factors to position Singapore as the largest seaport in the region. Singapore's container throughput showed signs of slower growth while ports in Malaysia, Indonesia, Thailand, and Vietnam signaled increasing growth (Woo et al., 2013; Woo et al., 2018). A possible reason is that from the perspective of the global value chain, multinational corporations have diversified their manufacturing facilities across the region; this makes these ports more integrated into global supply chains (Nguyen et al., 2020).

In particular, establishing the causal influence mechanisms underlying the observed correspondence between the structural-core organization and international trade of shipping network may require additional longitudinal network and economic data and methods on causal inference (Xu et al., 2020). The regression model is established from the perspective of geographic proximity, political proximity and economic proximity (Table.3). The regression results show that geographic proximity has a consistently significant positive effect, with the strongest influence observed during the colonial period. Colonial indicators are significantly positive during the colonial period, with their influence persisting in port community up to 1950. Indicators of whether or not they were in the same country, or the same region are significant from 1950 onwards and, in terms of the coefficients, the former has a large coefficient in the
post-WWII period, while the latter has a large coefficient in the 21st century, which is in line with the analysis described above. In terms of economic proximity, the amount of bilateral trade has a significant positive effect from the post-WWII period, and whether or not a bilateral trade agreement is signed has a positive effect after the 21st century. In addition, the difference in economic size between the two sides is not significant. In terms of the role of the three factors, political proximity is the dominant factor, geographic proximity is the fundamental factor, and economic proximity is the supporting factor.

<table><caption>Table 3 Regression results for port community model</caption><thead><tr><th>variables</th><th>Model 1890</th><th>Model 1910</th><th>Model 1930</th><th>Model 1950</th><th>Model 1970</th><th>Model 1990</th><th>Model 2000</th><th>Model 2008</th><th>Model 2016</th></tr></thead><tbody><tr><td>Distance</td><td>1.108**<br>(0.044)</td><td>8.471**<br>(0.022)</td><td>3.701***<br>(0.040)</td><td>0.201*<br>(0.019)</td><td>0.054***<br>(0.011)</td><td>0.006*<br>(0.008)</td><td>0.05***<br>(0.009)</td><td>0.065***<br>(0.008)</td><td>0.16***<br>(0.010)</td></tr><tr><td>Country</td><td></td><td></td><td></td><td>2.335***<br>(0.046)</td><td>15.15***<br>(0.031)</td><td>0.173<br>(0.142)</td><td>1.41***<br>(0.053)</td><td>1.39***<br>(0.044)</td><td>0.07<br>(0.132)</td></tr><tr><td>Region</td><td></td><td></td><td></td><td>1.226**<br>(0.052)</td><td>1.05***<br>(0.034)</td><td>1.29***<br>(0.039)</td><td>3.035***<br>(0.026)</td><td>1.57***<br>(0.030)</td><td>2.08***<br>(0.017)</td></tr><tr><td>Colony</td><td>1.299**<br>(0.156)</td><td>2.42**<br>(0.154)</td><td>1.38**<br>(0.177)</td><td>0.979*<br>(0.259)</td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Sibling</td><td>1.005*<br>(0.115)</td><td>0.699**<br>(0.132)</td><td>1.24**<br>(0.096)</td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Trade agreements</td><td></td><td></td><td></td><td></td><td></td><td>0.34<br>(0.165)</td><td>0.805***<br>(0.027)</td><td>0.976***<br>(0.028)</td><td>0.425**<br>(0.019)</td></tr><tr><td>Bilateral trade</td><td></td><td></td><td></td><td>0.32***<br>(0.008)</td><td>1.15**<br>(0.007)</td><td>0.042**<br>(0.002)</td><td>0.035***<br>(0.007)</td><td>0.131**<br>(0.003)</td><td>0.179***<br>(0.002)</td></tr><tr><td>GDP</td><td></td><td></td><td></td><td>0.049<br>(0.065)</td><td>1.47**<br>(0.031)</td><td>0.05<br>(0.038)</td><td>0.05<br>(0.054)</td><td>1.4**<br>(0.039)</td><td>0.048<br>(0.026)</td></tr><tr><td>Cons</td><td>1.74***<br>83</td><td>0.44***<br>96</td><td>0.77***<br>208</td><td>1.61**<br>270</td><td>0.67**<br>688</td><td>1.31**<br>1213</td><td>0.55**<br>1283</td><td>0.34**<br>1223</td><td>1.21***<br>2987</td></tr><tr><td>N</td><td>0.002</td><td>0.000</td><td>0.000</td><td>0.000</td><td>0.000</td><td>0.000</td><td>0.000</td><td>0.000</td><td>0.000</td></tr><tr><td>prob>chi2</td><td>0.283</td><td>0.299</td><td>0.231</td><td>0.286</td><td>0.356</td><td>0.333</td><td>0.428</td><td>0.427</td><td>0.554</td></tr><tr><td>R<sup>2</sup></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr></tbody></table>

Notes: *p < 0.1, **p < 0.05, ***p < 0.01; robust standard errors are in parentheses.

## 6 Conclusion

Based on 130 years of Lloyd's shipping data, this study analyzes the spatio-temporal evolution of port community structure in the Asia-Pacific shipping network, using complex network methods. Ports are grouped based on connectivity, and the evolution of hub ports and small-to medium-sized ports is examined across three key historical periods: colonial, post-WWII, and 21st-century.

In contrast to existing studies focusing on port evolution system from the perspective of whether ports are centralized or decentralized (Bird, 1963; Hayuth, 1981; Taaffe, 1963; Notteboom, 2005; Slack, 1990; Wilmsmeier and Monios, 2013), this study examines port fragmentation or integration within the shipping network, emphasizing port-to-port connectivity. This modular structure of the global ecosphere reflects the current trend of regionalization alongside globalization in international trade and the economy (Ducruet and Notteboom, 2012). Studies also note a concentration of global seaborne trade flows within regions (Xu et al., 2020). This paper extends and contributes to this perspective by examining a longer period and incorporating the viewpoint of port community evolution. From a methodological perspective, this study demonstrates the effectiveness of combining complex network analysis with historical maritime data to reveal long-term patterns of port integration
and fragmentation.

The analysis in section 4 supports the hypothesis that the Asia-Pacific region has undergone a process of regionalization, characterized by an increasing integration of communities with each other. Spanning the period from 1890 to 2016, the analysis of evolving community structure reveals two key trends supporting this hypothesis. Firstly, the number of ports and connections in the Asia-Pacific region increased rapidly while the number of communities decreased. Secondly, the analysis illustrates a gradual transition among ports from a fragmented pattern towards integration into four major communities. Subsequently, a stable “regionalization” community pattern emerged, characterized by four distinct communities: the Southeast Asian community centered around Singapore, the southern China port community with cores in Hong Kong and Shanghai, the northern China port community, and the Northeast Asia community centered around Busan. Based on the characteristics of port development and community evolution spanning 1890 to 2016, a four-phase evolutionary model can be abstracted and summarized: geographic proximity community, colony-dependency community, nationally bounded community, and transnational community.

Moreover, the maritime traffic flow exhibits a hierarchy where hub ports play a central role in network connectivity (Kanrak, 2019), with cargo transport relying mainly on the “hub port-hub port” connection (Guo et al., 2017). Over the past 130 years, the key hub ports in the Asia-Pacific region have shown a shift. The overall shipping network has evolved from a triangular pattern of Singapore-Hong Kong-Yokohama to a chain pattern of Singapore-Hong Kong-Shanghai-Busan. Meanwhile, bridge ports play crucial roles in connecting communities and promoting integration, including gateway ports and transshipment ports. The analysis also supports the hypothesis that the hub-feeder structure of East Asia from 1970 to 2000 (Robinson, 1998) is derived from more ancient patterns of maritime circulation in the region. Based on hub-feeder structure in this region, the Japanese ports, Hong Kong, and Singapore were key hubs from 1970 to the mid-1980s with Kaohsiung and Busan developing somewhat later in the period. This research confirms that the key hubs with Japanese ports, Hong Kong, and Singapore in the region date back to the early 20th century. Extending into the 20th century, the following conclusions still prove to be valid: The Japan-Singapore liner shipping corridor was focused on hub/feeder patterns in which Hong Kong and Singapore were the undisputed first order ports, while Kaohsiung and Busan played a somewhat lesser but nonetheless crucial role and the earlier dominance of Japanese ports - particularly Tokyo, Yokohama and Kobe - gradually eroded.

The region's shipping network is set against the intricate backdrop of a lengthy period marked by significant historical upheavals, including Western civilization and colonialism to economic modernization, and China's economic reforms. These transformative shifts have contributed to the region's unique and intricate nature. The development of Asian ports has been driven by the multidimensional role of the central government as port designers, developers, operators, pricing setters, and investors. Unlike the European and Anglo-Saxon Doctrine, the Asian Doctrine is dominated by the governments. Governments play an active role in improving port capacity and efficiency, which is a key feature behind the successful rise of Asian ports (Lee and
Flynn, 2011). Technological change and shipping line strategy are equally important factors influencing the evolution of port systems (Wilmsmeier et al., 2014). Between these two forces lie other factors, more at country level, such as free-trade agreements, colonial linkages, political proximities, etc. According to the analysis of different factors under the influence in the past 120 years, it is summarized as follows: political proximity is the dominant factor, geographic proximity is the fundamental, while economic proximity plays a supporting role.

The contribution involves both theoretical and empirical aspects. At the empirical level, utilizing unique and highly representative maritime ship movement data spanning over 130 years, this paper presents not only an empirical analysis but also innovates in its systematic exploration of maritime transportation networks in the Asia-Pacific region. These findings provide empirical support for the notion of regionalization within the Asia-Pacific maritime network, highlighting the emergence of cohesive community structures and the evolving dynamics of integration over time. At the theoretical level, this paper takes a first step in this direction by summarizing port community evolution model which reveals the status of port fragmentation or integration for more than 120 years. Together, these contributions not only advances the understanding of global shipping networks in academic research but also offers valuable insights into the strategic roles of ports and the operational dynamics of major shipping companies and policymakers.

In the future, as hierarchical structures, and networking of ports in the Asia-Pacific shipping network continue to develop, the role of large hubs, transshipment ports, and feeder ports will become increasingly well-defined. First, the integration of ports within the region that breaks through national boundaries is an inevitable trend, with port community evolution favoring large-scale regionalization. The “regional effect” remains significant, underlining the continuing relevance of the comparative analyses of freight transport systems (Rodrigue and Notteboom, 2010). Owing to the historical specificity of the Asia-Pacific region, comparative research is needed to highlight similar trends in other regional port systems. Second, while this study primarily analyzes shipping links of total cargo types, future research can explore the evolution of port communities across different cargo types, leading to further discoveries. Third, while Lloyd's List offers unparalleled historical coverage over more than a century, it lacks the spatial precision and real-time tracking capabilities of modern AIS (Automatic Identification System) data. In recent years, the emergence of AIS data has greatly advanced maritime network studies by enabling fine-grained, real-time analysis of vessel trajectories and port interactions (LaRock, 2022). Future studies could leverage AIS data and other port- and shipping-related big data to complement historical sources such as Lloyd's List. By integrating trade, political, and shipping networks through multilayer network analysis methods, future research could more accurately capture the dynamic evolution of maritime communities and enhance the prediction of future community patterns in the Asia-Pacific region.
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