Paywalls Down, Impact Up: An Overview of Participation of HKU Authors in Open Access Publishing 2025
— by Fanny Liu
Introduction
Similar to last year’s post, this post presents an overview of open access publications authored by researchers of the University of Hong Kong (HKU) for 2025.
Data
Publication and Category Normalized Citation Impact (CNCI) data were extracted from InCites (data from the Web of Science Core Collection) on 21 January 2026. For the purpose of this report, publications included only articles and reviews indexed in the InCites Dataset (with ESCI) affiliated to “University of Hong Kong”. All Open Access encompassed Gold (including Gold-hybrid), Green, and Bronze (Free to read) Open Access.
Altmetrics data were retrieved on 21 January 2026 with Altmetric Explorer.
All Open Access
Researchers at HKU committed to making research outputs open access. The percentages of all open access from 2006 to 2025 displayed an evident general upward trend, despite short periods of plateau and decline (Figure 1). From 2006 (20.07%) to 2025 (53.65%), open access ratios more than doubled. Specifically, the open access document ratio slightly dropped to 51.78% in 2024, as compared to 53.76% in 2023, and in 2025, the ratio increased to 53.65%. This might be attributed to 1) during COVID-19, to accelerate research on COVID-19, various publishers making the research articles freely accessible and authors disseminating research findings via preprinting, and 2) after COVID-19, academics’ enhanced awareness of open access (Besançon et al., 2021; Turgut et al., 2022).
Figure 1: Percentage of All Open Access HKU Publications by Year (2006-25)
Gold and Green Open Access
The ratio of gold (including gold-hybrid) open access publications continued to increase when that of green-only open access decreased (Figure 2). This may partly be driven by the growing number of Transformative Agreements between the Libraries and publishers, which enabled HKU corresponding authors to make their publications gold open access in thousands of eligible journals without paying the charges by themselves; For example, in 2025, new agreements with Elsevier and Oxford University Press were in effect, covering eligible journals.
Figure 2: Percentage of Gold (Including Gold-hybrid), Green Only and All Open Access HKU Publications by Year (2006-25)
Publishers and Journals
In 2025, the most popular publisher with which HKU authors published in open access remained Springer Nature, accounting for 801 publications, followed by Elsevier and Wiley, with 600 and 391 publications, respectively. See Figure 3.
As for individual journal titles, the five most popular titles were Nature Communications (118 publications), Advanced Science (68 publications), Scientific Reports (64 publications), International Dental Journal (43 publications) and Science Advances (33 publications). All five journals were fully open access journals which did not accept publishing behind the paywall. As of 21 January 2026, only Advanced Science (Wiley) was covered by a transformative agreement. Nature Communications (Springer Nature), Scientific Reports (Springer Nature) and International Dental Journal (Elsevier) were not eligible under the agreement with Springer Nature and Elsevier, respectively, as “prestigious” and open access journals were excluded from the agreement. Currently, no transformative agreement was available between the Libraries and the American Association for the Advancement of Science (AAAS). This demonstrated the limitation of current transformative agreements, mainly caused by the lack of funding support.
Figure 3: Gold (Including Gold-hybrid) Open Access HKU Publications by Publisher and Journal in 2025
Citation Impact
The Category Normalized Citation Impact (CNCI) is the number of citations received a publication divided by the expected citations for publications with the same document type, year of publication, and subject area. For a publication set, the CNCI value is the arithmetic mean of the individual CNCI values for each publication.
The CNCI values of HKU publications were always higher than the world average (1) from 2021 to 2025. Among them, open access publications consistently achieved higher citation impact than non-open access ones. See Figure 4.
In 2025, the citation impact of green open access publications was greater than gold (including gold-hybrid) ones.
Figure 4: CNCI of All Open Access, Gold (Including Gold-hybrid), Green Only and Non-Open Access HKU Publications by Year (2021-25)
Altmetrics
Among the open access publications with a DOI (digital object identifier) published by HKU authors in 2025 indexed by InCites and tracked by Altmetric Explorer, 81.71% received Altmetric attention, higher than 68.67% of the non-open access ones. On average, open access publications received an Altmetric Attention Score of 16.68, while non-open access ones, 12.32. This might show that open access publications in general attract more attention and discussion on social media, news, policies, and other online platforms.
The five non-open access and open access publications receiving the highest Altmetric Attention Scores are shown in Table 1.
| Non-open access | Open access |
|---|---|
| Long-term impacts of heatwaves on accelerated ageing | Global, regional, and national trends in routine childhood vaccination coverage from 1980 to 2023 with forecasts to 2030: a systematic analysis for the Global Burden of Disease Study 2023 |
| The mutagenic forces shaping the genomes of lung cancer in never smokers | Global, regional, and national prevalence of adult overweight and obesity, 1990-2021, with forecasts to 2050: a forecasting study for the Global Burden of Disease Study 2021 |
| The Lancet Commission on addressing the global hepatocellular carcinoma burden: comprehensive strategies from prevention to treatment | The impact of childhood trauma and cannabis use on paranoia: a structural equation model approach |
| Are anxious Mondays associated with HPA-axis dysregulation? A longitudinal study of older adults in England | A brain-wide map of neural activity during complex behaviour |
| 300,000-year-old wooden tools from Gantangqing, southwest China | Genetic Susceptibility to Type 2 Diabetes, Television Viewing, and Atherosclerotic Cardiovascular Disease Risk |
Table 1: Five non-open access and all open access publications receiving the highest Altmetric Attention Scores
Conclusion
In summary, open access publications continued to grow over the past years. The citation impact and altmetric attention of open access publications were higher than those of non-open access ones. Green open access publications in general achieved higher citation impact.
HKU researchers can use the support from the Libraries for them to publish open access, including:
- Green open access: Deposit Accepted Manuscripts to HKU Scholars Hub via Research Information Management System (RIMS).
- Gold open access: Check Libraries’ transformative agreements to see coverage of open access fees.
References
Besançon, L., Peiffer-Smadja, N., Segalas, C., Jiang, H., Masuzzo, P., Smout, C., Billy, E., Deforet, M., & Leyrat, C. (2021). Open science saves lives: Lessons from the COVID-19 pandemic. BMC Medical Research Methodology, 21(1), 117. https://doi.org/10.1186/s12874-021-01304-y
Turgut, Y. E., Aslan, A., & Denizalp, N. V. (2022). Academicians’ awareness, attitude, and use of open access during the COVID-19 pandemic. Journal of Librarianship and Information Science, 54(3), 350–362. https://doi.org/10.1177/09610006211016509
Declaration of Generative AI use
I acknowledge the use of Generative AI tools in writing this post. I used:
- GPT-5.2 to brainstorm ideas for the post title.
- GPT-5.2 to check for grammar mistakes and typos in the content I wrote.
I declare that I reviewed and edited the contents as needed, and take full responsibility for the contents of the post; And the information provided is complete and accurate.
