Earlier this year, the scientific journal PLoS ONE published their 10,000th article. Ten thousand articles is a lot of papers especially when you consider that PLoS ONE only started publishing four short years ago in 2006. But scientists have been publishing in journals for at least 350 years  so it might make you wonder, how many articles have been published in scientific and learned journals since time began?
If we look at PubMed Central, a full-text archive of journals freely available to all – PubMedCentral currently holds over 1.7 million articles. But these articles are only a tiny fraction of the total literature – since a lot of the rest is locked up behind publishers paywalls and is inaccessible to many people.
PubMed, a freely available index of biomedical abstracts published by the National Center for Biotechnology Information has a collection of more than 19 million citations. Nineteen million is hard to comprehend but around one paper per minute* is added to this database (on average) and this is an easier number to understand. But even this enormous database excludes large swathes of published articles in Physics, Mathematics, Chemistry, Engineering and Computer Science not deemed “worthy” of indexing by the United States National Library of Medicine. Neither does it include all the humanities publications – PubMed is not the world ®.
Next up, Scopus, a subscription-only database of journals covers a wider range of literature than PubMed and currently claims to have indexed over 40 million records. A rival of Scopus, ISI Web of Knowledge (WOK), claims to be a similar size with 40 millon items. But again like PubMed, Scopus and WOK are not the world. Google Scholar which is currently trying to take over the world, indexes all this data too, but they don’t say how big their index is .
Finally, Arif Jinha at the University of Ottawa has recently estimated that the number of journal articles published since time began is about 50 million . This estimate is based on what has been published since 1665 when the journal Philosophical Transactions of the Royal Society first started. The 50 million article estimate has recently been published in Learned Publishing . It’s debateable how accurate the estimate is, since its actually quite tricky to work out, but 50 million is still a big number to get your head around. Perhaps its easier to think of 50 million papers like this:
- One paper for every base-pair in human chromsome Y
- One paper per tweet at twitter on an average day in 2010
- One paper for each year that modern mammals have been roaming the earth (at least according to wikipedia)
- One paper per resident of England
- One paper per [insert your favourite 50 million anecdote here]
So how many journal articles have been published (ever)? It depends on what you mean by “journal”, “article”, “published” and “ever” – and these terms are taking on new meanings since the invention of the Web. But for the definitions used in  an estimate of 50 million seems reasonable, plus or minus a few million.
- Henry Oldenburg (1665). Epistle Dedicatory Philosophical Transactions of the Royal Society of London, 1 (1-22) DOI: 10.1098/rstl.1665.0001
- Peter Jacsó (2010). Metadata mega mess in Google Scholar Online Information Review, 34 (1), 175-191 DOI: 10.1108/14684521011024191
- Arif Jinha (2010). Article 50 million: an estimate of the number of scholarly articles in existence Learned Publishing, 23 (3), 258-263 DOI: 10.1087/20100308 free pre-print available from author here
* One paper per minute is based on 679,858 papers per year in 2009 / 365 days / 24 hours / 60 minutes = 1.29 papers per minute. The PubMed database isn’t updated that frequently, but if it was, there would be 1.29 papers added per minute according to MEDLINE statistics.