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Since the Nature Index launched in 2014, one noticeable trend over time has been that the number of articles in the database has stayed reasonably consistent each year. It has still grown — in 2023, there were almost 78,000 articles tracked, up from just below 60,000 in 2015. But part of this can be explained by changes in the list of journals, especially the addition of health sciences in 2022.
In 2024, however, there was a big jump of 16.1% to just over 90,000 articles, the largest year-on-year rise in volume in the database’s 10-year history. Given that the set of 145 journals tracked in 2023 and 2024 was the same, this is worth exploring.
In an area as complex as research publishing, it’s difficult to be conclusive, but there are a few factors to consider.
First, digging into the data on individual journals shows that there have been some big percentage increases in the number of articles published, including at titles with a large footprint in the database.
Nature Communications, for example, published around 2,200 more articles that were included in the database in 2024 compared with 2023, meaning its Nature Index article count rose by 28% (only primary research articles are added to the database, so not all papers in a journal may be included).
Other large journals tracked by the Nature Index that had big year-on-year rises in articles in the database include Advanced Functional Materials, up 54%, and Angewandte Chemie International Edition, up 45%, both published by Wiley (Nature Index contains journals run by a number of publishers). There are other journals that have seen even heftier percentage increases, but often these are relatively small journals that won’t make a huge difference to the overall size of the database.
The reasons some journals saw such an uplift are much more difficult to pin down. One possibility is that certain research areas are seeing rapid growth.
The Nature Index citation topics pages — which show trends in the database for research areas defined by citation networks — suggest that areas with particularly big increases in article volume, especially in the past two years, include physical chemistry, chemical engineering, macromolecular and materials chemistry, and materials engineering.
These topics are closely related to the development of next-generation green technologies, such as electric-vehicle batteries and carbon-dioxide conversion – areas of research that are increasingly popular. The Nature Index supplement on materials science, published in December, showed that from 2019 to 2023, there was a 25% increase in the number of articles in the index related to materials science, representing 27.2% of all research in the database in 2023.
With some of the journals mentioned above focused on publishing materials or chemistry research, it is therefore no surprise to see the index as a whole expanding. For instance, of the 4,722 Angewandte Chemie International Edition articles that were indexed in the database in 2024, almost 42% were in two topic areas: physical chemistry, and macromolecular and materials chemistry.
Data from the Digital Science Dimensions database also suggest large multi-disciplinary journals such as Nature Communications are seeing high growth rates in these fields. Of the five biggest fields by article volume in the journal in 2024, the highest annual growth rates were seen in engineering (40%), chemical sciences (35%) and physical sciences (30%).
Another potential factor is growing article output from particular countries and regions, such as China, that concentrate a high proportion of their research on these fields. The materials-science example is again useful here. In 2023, China, Japan, South Korea, India and Singapore were all among the global top 10 for Nature Index output in materials research and together contributed to 63% of the database’s total output in the subject. All five of these Asian nations, except Japan, also increased their relative output in the database from 2023 to 2024, in the case of China by 17%.
So not only are certain subjects increasing their footprint in the database, there is also an increase in output from some parts of the world, especially China, that specialize in these fields (indeed, 46% of China’s output in the database in 2023 was in materials science).
A further consideration is that research publishing is on an upward trajectory generally, reflecting a growth in global funding for science. Data from Dimensions suggest that the total number of research articles (not including preprints or conference proceedings) went up 7% from 2023 to 2024 and almost doubled from 2016 to 2024. A major reason for these increases is the creation of new journals, and the growth of publishing models such as open access, rather than extra articles in the same subset of publications, but it is still likely to be a factor in Nature Index article growth.
Finally, a growing database could also reflect shifts in where researchers are publishing. If there is any move towards publishing in Nature Index journals from publications outside the database then this could increase volume. The figures on this are very hard to pin down and quantify, and would need an extensive analysis at the journal level. However, at a publisher level it has been noticeable that two companies specializing in open-access research — MDPI and Frontiers — have had falls in overall publication output since 2022 after years of rapid growth. It is possible, therefore, that these market adjustments have impacted Nature Index volume in some way.
So, numerous factors need to be taken into account in looking at why the article volume in the Nature Index grew by 16% in 2024. But with any year-on-year comparisons of output by institutions or countries — such as in this year’s Research Leaders tables — it’s worth pointing out that the metric ‘adjusted Share’ is used to account for changes in article volume, even when there is a rise as large as this one.
