Sci-Hub remains among the most common sites via which readers circumvent article paywalls and access scholarly literature. But where exactly are its download requests coming from? And just what is being downloaded? Bastian Greshake has analysed the full Sci-Hub corpus and its request data, and found that articles are being downloaded from all over the world, more recently published papers are among the most requested, and there is a marked overrepresentation of requested articles from journals publishing on chemistry.

Free and open access to the academic literature is still a hot issue, as the output of academic publishing remains largely behind paywalls, hindering researchers and the general public alike in their efforts to read the latest research. Thanks to the tireless efforts of the open access movement about 25% of scholarly documents on the web are now accessible through some form of open access, and recent initiatives like Unpaywall, a browser extension that looks to find open access versions of a given article, make it even easier to get access.

One of the most (in)famous ways to circumvent paywalls around scholarly literature is Sci-Hub, the website of dubious legality which offers free access to around 62 million academic articles at the click of a button. While Elsevier is trying to establish the illegality of the service in court, many articles have been written about the morality behind the site and how it’s a symptom of a failing publishing system.

In 2016, John Bohannon collaborated with Sci-Hub founder Alexandra Elbakyan on a first exploration of “who is using Sci-Hub?”. Looking at six months’ worth of data, totalling 28 million download requests to Sci-Hub, the answer was a resounding “everyone”, with downloads coming from all over the globe. The public release of the data enabled further analysis showing that, while the country-wide use of Sci-Hub correlates with population size, there are some clear outliers. Iran, which has long suffered from international sanctions affecting access to academic journal subscriptions, shows a large number of requests to Sci-Hub, as does Greece, which continues to struggle with unemployment and economic hardship. Additionally this analysis showed that around 8% of all download requests come from inside academic institutions around the globe, hinting that access through university libraries is far from universal.

Figure 1: How countries differ in the observed download requests from the expected requests given a linear regression over the population size. Please click here for an enlarged version of this figure. (Available under a CC0 1.0 Public domain dedication).

Figure 2: Percent of download requests made from academic institutions over time, points are coloured by weekdays. Please click here for an enlarged version of this figure. (Available under a CC0 1.0 Public domain dedication).

In March 2017, Sci-Hub released a list of the 62 million articles in its database. This allowed for a comparison of how the downloaded articles differ from the background set of all available articles. Looking at the age distribution of the publications in the complete Sci-Hub corpus shows how the speed of scientific publishing has picked up. Since the early 1900s the number of publications per year rises quickly, with two notable exceptions being the periods of the two world wars, as denoted by red lines in the top graph of Figure 3. At the end of each war the scientific output was set back to levels of about 10 years before the war’s beginning.

Figure 3: The age of articles in the corpus (top) and of articles that are being requested (bottom). Please click here for an enlarged version of this figure. (Available under a CC0 1.0 Public domain dedication).

Compared to this null distribution the age of papers requested for downloads leans heavily towards newer publications. In fact, 35% of requested papers are younger than two years’ old at the time of the request. This provides further evidence that embargoes, where publishers don’t allow free access to published articles for a period up to 24 months, are ineffective, as readers just move around the paywalls.

The analysis of which journals are being requested from Sci-Hub shows a surprising effect when comparing it to the total distribution of publications by journal. While the big, interdisciplinary journals, like Nature and Science, make the top 20 list of most requested journals, as one would expect given their publishing volume, there is a marked overrepresentation of journals publishing on chemistry, with 12 of the 20 most requested journals coming from the discipline. Meanwhile, biomedical journals appear less. This seems indicative of how these different fields operate and how they access the scientific literature; while 50% of chemistry graduates and 58% of engineering graduates move into private, for-profit industry and only 32% and 27% respectively stay at educational institutions, the numbers are virtually reversed for the life sciences, with 52% of graduates staying at educational institutions.

Figure 4: Top journals in the complete Sci-Hub corpus (top) and top journals that are being requested for downloads (bottom). Red bars denote chemistry journals. Please click here for an enlarged version of this figure. (Available under a CC0 1.0 Public domain dedication).

Lastly, analysing Sci-Hub at a publisher level shows the full extent of the oligopoly that is the current scholarly publishing business. Of 1769 publishers only 201 have articles being downloaded through Sci-Hub more than would be expected given their publishing volume, while over half are downloaded less. And amongst those that are downloaded more than expected are giants like Elsevier and Springer Nature. In fact, close to 50% of all articles requested from Sci-Hub are published by just three companies.

Figure 5: Top publishers represented in the Sci-Hub corpus (top) and in the download requests (bottom). Please click here for an enlarged version of this figure. (Available under a CC0 1.0 Public domain dedication).

By looking into how and where Sci-Hub is used it becomes clear that barriers to access to scholarly publications remain a real issue, one that is affecting a diverse group of actors in many different ways. And thanks to a so-far unbroken oligopoly in academic publishing, with a small set of commercial actors dominating the market and setting the terms to access, this is unlikely to change very soon. Thus, issues of legality aside, Sci-Hub remains a strong route to education for researchers from states suffering from international embargoes or economic hardship just as it is for individuals outside academic institutions everywhere else in the world.

If you want to explore the data on Sci-Hub yourself, have a look at this small web application (still in development), which allows you to browse the data easily.

This blog post is based on the author’s article, “Looking into Pandora’s Box: The Content of Sci-Hub and its Usage”, published in F1000Research (DOI: 10.12688/f1000research.11366.1).

Featured image credit: ? by Alistair Hamilton (licensed under a CC BY 2.0 license).

Note: This article gives the views of the author, and not the position of the LSE Impact Blog, nor of the London School of Economics. Please review our comments policy if you have any concerns on posting a comment below.

About the author

Bastian Greshake is a biologist-turned-bioinformatician, currently working on his PhD in the Group for Applied Bioinformatics at the University of Frankfurt. Besides his research in fungal genomics he has a strong interest in open science and all things open. In 2011 he co-founded openSNP, an award-winning citizen science project that creates open data by putting personal genetics data into the public domain. In addition he does research into how people get around the barriers that prevent them access to research outputs. He tweets at @gedankenstuecke.