Research on Evolution Characteristics and Factors of Nordic Green Patent Citation Network
Abstract
:1. Introduction
2. Literature Review
3. Data Sources and Research Methods
3.1. Data Collection and Processing
3.1.1. Data Sources and Retrieval Strategies
3.1.2. Data Analysis
3.2. Social Network Analysis
3.2.1. Topological Network Analysis
- Network scale: It refers to the number of nodes and edges in the network, indicating the coverage scale of the network.
- Average degree: It refers to the average number of connections between any node in the network and other nodes, including the out-degree (the number of times it is cited by other nodes) and the in-degree (the number of times it is citing other nodes), indicating the influence range of network nodes.
- Network diameter: It refers to the maximum value of the shortest path between any two nodes in the network, indicating the reach-ability between nodes.
- Average path length: It refers to the average value of the shortest path between any two nodes in the network, indicating the accessibility, transitivity, and connectivity of nodes.
- Clustering coefficient: It refers to the degree of interconnection between adjacent nodes of a node. For a single node, the clustering coefficient is the ratio of the actual number of connected edges between its adjacent nodes to the number of edges connected when all adjacent nodes are connected to each other. For the overall network, the clustering coefficient value is the average of the clustering coefficients of a single node. In order to study the characteristics of the overall network, this paper adopts the overall network clustering coefficient, which reveals the degree of aggregation between network nodes.
- Connected component: It refers to the number of weakly connected independent sub-networks in the network, indicating how many small groups that are more closely connected exist in the network.
3.2.2. Analysis of Key Nodes
3.2.3. Core Network Analysis
3.3. Exponential Random Graph Model and Variable Selection
3.3.1. Research Model Construction
3.3.2. Selection of Model Variables
4. Result Analysis
4.1. Evolution Characteristics of Nordic Green Patent Citation Network
4.1.1. Evolution Analysis of Topological Network
4.1.2. Evolution Analysis of Key Nodes
4.1.3. Evolution Analysis of Core Network
4.2. Influencing Factors of Nordic Green Patent Citation Network
4.2.1. Model Estimation
4.2.2. Analysis of Parameter Estimation Results
- (1)
- The influence of network endogenous structure variables on the Nordic green patent citation relationship is relatively stable.
- (2)
- The node attribute variables that have an impact on the Nordic green patent citation relationship are gradually increasing.
- (3)
- The influence of node relationship covariates on the Nordic green patent citation relationship is gradually significant.
4.2.3. Robustness Test
5. Conclusions and Prospects
5.1. Research Conclusions
- (1)
- The technological fields involved in the patent citation network extend from the traditional wastewater and waste gas treatment to the utilization of clean energy and gradually interact with artificial intelligence. In other words, the development of the Nordic green industry has gradually changed from passive development to active innovation, indicating a change in its green development concept.
- (2)
- More relatively independent small groups are formed in the network, and a certain clustering effect is formed among patents of the same technological subject. With the passage of time, the number of small groups gradually increases, indicating that the technological subjects involved in Nordic green patents are increasingly diversified.
- (3)
- The core network shows an obvious cluster distribution, and the increase in the number of clusters indicates that the fields involved in core patents are becoming more and more abundant. The star topology in the clusters also indicates that there is a certain “propensity link” phenomenon for core patents.
- (1)
- The Nordic green patent citation network has good connectivity and transitivity, always maintains a closed triangular structure, and is relatively stable in the evolution process.
- (2)
- The regional heterogeneity effect is always significant, and there is still space for long-distance technology diffusion. Nordic green industry-related patents always tend to form citation relationships with the relevant patents outside the region, and they do not exclude the exchanges and cooperation with countries or regions outside the region in green technology. And after the technology gradually matures, its diffusion range will gradually expand.
- (3)
- The nodes in the network tend to cite highly cited patents, but the connection between highly cited patents is not close. With the patent network gradually showing the trend of diversification and differentiation, several “small groups” have been formed gradually. The “Star patents” within the small groups are more likely to be cited, but the connection between different “small groups” is not close.
- (4)
- The higher the awareness of patent property protection, the more conducive to promoting the formation of patent citation relationship. No matter further improving patent claims or laying out patents in multiple patent offices, the deepening awareness of patent property protection can both be reflected. With the gradual standardization of the patent application process, patent applicants will be more inclined to adopting an active information disclosure strategy to avoid being in a disadvantageous position in litigation that may arise later due to incomplete information disclosure [58], which will further improve the probability of forming patent citation relationship.
- (5)
- In the process of technology diffusion, the integration of industry and academia is conducive to the formation of green patent citation relationship. In the development of Nordic green patents, the substitution effect between non-patent documents and patent documents has gradually weakened and the complementary effect has increasingly strengthened, and the integration of industry and academia has promoted the development of patent citation network.
5.2. Policy Implications
- (1)
- Strengthen industry–university cooperation.
- (2)
- Enhance the protection of patent property rights.
- (3)
- Strengthen international technological exchanges and cooperation.
5.3. Research Prospect
- (1)
- The research sample has certain limitations and can be further expanded in the follow-up study. The analysis of the green patent citation relationship in this paper mainly studies the Nordic countries. When selecting the research object, this paper mainly takes into account the environmental vulnerability of the Nordic region and the progressiveness of green industry development. However, when processing the data, it is found that the United States, Germany, Japan, and other countries also have outstanding performance in the technological development of the green industry. In the subsequent study, the scope of the research objects and the corresponding sample collection can be further expanded to include other countries with better development of green industries and countries with greater development potential.
- (2)
- The study of influencing factors still has limitations, and more variables can be included for discussion. In this paper, when studying the factors influencing the formation of patent citation relationship, several factors concerning endogenous structure, node attributes, and node relationship covariates have been included for discussion, but still not to the extent of being comprehensive. In the subsequent research process, more variables can be included in the ERGM for more comprehensive analysis and discussion.
Author Contributions
Funding
Institutional Review Board Statement
Informed Consent Statement
Data Availability Statement
Conflicts of Interest
References
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Nordic Green Patents | Cited Patents | Average Cited Patents | Citing Patents | Average Citing Patents | |
---|---|---|---|---|---|
1980–1989 | 956 | 1622 | 1.70 | 12,660 | 13.24 |
1990–1999 | 1184 | 5182 | 4.38 | 15,554 | 13.14 |
2000–2009 | 1600 | 12,387 | 7.74 | 20,157 | 12.60 |
2010–2019 | 4012 | 28,936 | 7.21 | 8812 | 2.20 |
Type of Variables | Variables | Annotations |
---|---|---|
Network endogenous structure variables | edges | The constant term of the model which is equivalent to the network density, and reflects the basic tendency of the network nodes to form relationships |
twopath | The open triangle structure that patent I cites patent j and patent j cites patent k, indicating the connectivity of the patent citation network | |
transitiveties | The closed triangle structure that patent I cites patent j, patent j cites patent k, and patent I cites patent k, reflecting a certain degree of transitivity | |
gwodegree | The distribution of the nodes’ out-degree, which can reflect the activity of nodes in the network | |
Node attribute variables | nodecov.claims | The number of patent claims, representing the scope of protection given by the patent or patent application in scientific terms which mainly reflects the boundary of technology exclusivity |
nodecov.references | The number of citations to scientific and technological documents other than patent documents which shows the dependence of patents on existing technologies | |
nodecov.family | The size of the patent family, that is, the number of patents of the same family, reflecting the patent value | |
absdiff.region | Whether the country of the first applicant of the patent is a Nordic country, reflecting the heterogeneous effect of geography | |
nodematch.cited | Frequency of patent cited, reflecting the homogeneous effect of cited frequency and the “rich club” phenomenon | |
Node relationship covariates | edgecov.field | Whether there is a similarity in the technological field between different nodes. If the technological fields of patent I and patent j are the same, the value is assigned to 1, otherwise, the value is assigned to 0 (the first four digits of the main IPC number of the patent are classified as a technological field [52]) |
edgecov.year | Time difference between different patent publication years | |
edgecov.distance | The distance between countries to which different patents belong |
Number of Nodes | Number of Edges | Average Degree | Network Diameter | Average Path Length | Clustering Coefficient | Connected Component | |
---|---|---|---|---|---|---|---|
1980–1989 | 12,692 | 14,097 | 1.111 | 5 | 1.754 | 0.010 | 440 |
1990–1999 | 17,745 | 20,473 | 1.154 | 5 | 1.997 | 0.010 | 516 |
2000–2009 | 25,983 | 32,255 | 1.241 | 6 | 1.974 | 0.013 | 591 |
2010–2019 | 29,449 | 36,866 | 1.252 | 7 | 1.843 | 0.016 | 1551 |
1980–1989 | 1990–1999 | 2000–2009 | 2010–2019 | |||||
---|---|---|---|---|---|---|---|---|
Hubs | Authorities | Hubs | Authorities | Hubs | Authorities | Hubs | Authorities | |
1 | 4889698A | 7361209B1 | 5024685A | 7833322B2 | 4477690A | 6465979B1 | 6255793B1 | 10433697B2 |
2 | 4273747A | 8034163B1 | 5993521A | 7724492B2 | 5545853A | 6873080B1 | 7332890B2 | 10209080B2 |
3 | 4233274A | 7731780B1 | 5012159A | 7767169B2 | 4357542A | 6891303B2 | 7613543B2 | 10149430B2 |
4 | 4443417A | 6855859B2 | 5180404A | 7077890B2 | 4565929A | 7061133B1 | 8396592B2 | 9295362B2 |
5 | 4583999A | 8293196B1 | 4955991A | 7638104B2 | 4853565A | 6525265B1 | 7761954B2 | 9405294B2 |
1980–1989 | 1990–1999 | 2000–2009 | 2010–2019 | |
---|---|---|---|---|
edges | −3.013 *** | −3.801 *** | −6.362 *** | −4.916 *** |
(0.249) | (0.183) | (0.133) | (0.081) | |
nodeicov.claims | −0.001 | 0.007 *** | 0.007 *** | −0.009 *** |
(0.003) | (0.002) | (0.001) | (0.002) | |
nodeocov.claims | −0.008 | −0.018 *** | −0.008 *** | −0.001 |
(0.004) | (0.003) | (0.002) | (0.001) | |
nodeicov.references | −0.002 ** | −0.003 *** | 0.002 *** | 0.002 *** |
(0.001) | (0.001) | (0.001) | (0.001) | |
nodeocov.references | −0.014 | −0.067 *** | −0.010 *** | −0.001 |
(0.011) | (0.011) | (0.001) | (0.001) | |
nodeicov.family | −0.006 | 0.007 ** | 0.013 *** | 0.006 *** |
(0.005) | (0.002) | (0.001) | (0.001) | |
nodeocov.family | 0.003 | −0.001 | −0.020 *** | 0.008 *** |
(0.003) | (0.003) | (0.002) | (0.001) | |
absdiff.region | 0.688 *** | 1.022 *** | 3.128 *** | 0.582 *** |
(0.152) | (0.124) | (0.087) | (0.039) | |
nodematch.cited | 0.138 | −0.043 | −0.255 *** | −1.417 *** |
(0.094) | (0.073) | (0.058) | (0.081) | |
gwodeg | −4.973 *** | −2.886 *** | −2.450 *** | −0.686 *** |
(0.472) | (0.349) | (0.155) | (0.135) | |
twopath | −0.456 *** | −0.305 *** | −0.088 *** | −0.372 *** |
(0.046) | (0.021) | (0.004) | (0.012) | |
transitiveties | 1.624 *** | 1.678 *** | 1.520 *** | 2.542 *** |
(0.083) | (0.052) | (0.053) | (0.072) | |
edgecov.field | −0.109 | 0.069 | −0.043 | 0.001 |
(0.096) | (0.066) | (0.058) | (0.044) | |
edgecov.distance | 0.437 | −0.107 | −0.067 | 0.292 *** |
(0.269) | (0.222) | (0.100) | (0.081) | |
edgecov.year | −0.003 | 0.006 | −0.008 | 0.011 *** |
(0.006) | (0.006) | (0.006) | (0.003) | |
AIC | 3907 | 10,175 | 32,449 | 37,892 |
BIC | 4029 | 10,317 | 32,618 | 38,067 |
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Li, Z.; Wang, Y.; Deng, Z. Research on Evolution Characteristics and Factors of Nordic Green Patent Citation Network. Sustainability 2022, 14, 7743. https://doi.org/10.3390/su14137743
Li Z, Wang Y, Deng Z. Research on Evolution Characteristics and Factors of Nordic Green Patent Citation Network. Sustainability. 2022; 14(13):7743. https://doi.org/10.3390/su14137743
Chicago/Turabian StyleLi, Zhenfu, Yixuan Wang, and Zhao Deng. 2022. "Research on Evolution Characteristics and Factors of Nordic Green Patent Citation Network" Sustainability 14, no. 13: 7743. https://doi.org/10.3390/su14137743