This month we examine how the growth of the Directory of Open Access Books (DOAB) has developed over the last 18 months. We look at some key statistics from the Directory and examine the continuing growth in OA Books.


The Directory of Open Access Books (DOAB) tracks academic books, which “must be made available under an open access licence and be subjected to independent and external peer review prior to publication”. It is a useful proxy for how the OA books market is developing.

We have previously analyzed how it was growing and its composition. Around 18 months later, we update our analysis to see how things have changed.

Growth of the DOAB

The DOAB now claims to have well over 60,000 titles, and continues to grow. The chart below shows how the index has grown.

Source: DOAB, Delta Think Analysis. © 2023, Delta Think Inc. All rights reserved.

The chart above shows the cumulative number of titles and publishers growing over time.

  • The number of titles has doubled since our last analysis, to just over 60,000 from around 500 publishers1.
  • There was a 17% year-on-year growth in the number of titles from 2021 to 2022.
  • The rate of growth is slowing: The 5-year CAGR from 2017-2022 is around 36%.
  • There are now 525 publishers registered in the index, up from around 490 at the time of our last analysis.
  • As with the number of indexed titles, the number of publishers continues to grow, but at a slowing rate.
  • Our previous analysis excluded titles with an unspecified Indexed year. Our current analysis includes all titles, using their publication year as a proxy for their indexed year if the latter is not specified.

Leading publishers using the DOAB

The chart below analyses the larger contributors of data to the DOAB.

Source: DOAB, Delta Think Analysis. © 2023, Delta Think Inc. All rights reserved.

The figure above shows the cumulative number of titles added to the index over time by the top 10 publishers.

  • The books market is consolidated: The top 10 publishers account for around 48% of total output.
  • Consolidation has been increasing, with the top publishers taking increasing share over time. From 2018, the few larger publishers have increasingly started to dominate.
  • Around 16% of the records do not specify when the book was added to the index. (These are shown in the right-most column.) This speaks to some issue either with publishers’ deposition of metadata or the indexing itself. A subset of the larger publishers covers a disproportionally large share of these unknown years.

DOAB Largest Publishers Analyzed by License Type

Publishers deposit information about books retrospectively.

Source: DOAB, Delta Think Analysis. © 2023, Delta Think Inc. All rights reserved.

The chart above analyses share of output by year of book publication, rather than the year in which a book’s metadata was indexed.

  • Again we see a consolidated market. For titles published in 2022, the 10 largest publishers together account for around 43% of the index.
  • Consolidation by year of publication has slowly increased until 2021, but is showing signs of reversing. It’s too soon to tell if this is a reversal in trend or just a one-off.
  • Across all years, IntechOpen remains the largest publisher (9.6% share), followed by MDPI (8.5%) and then de Gruyter (4.8%).
  • Another 595 or so publishers lie outside the top 10.


The DOAB continues to see strong growth, and continues to outpace the growth in journals. Over the 5 years to 2022, its CAGR was 34%, compared with 22% for OA journal articles.

Growth has previously been driven by larger organizations coming on board, plus a growing long tail of publishers joining OAPEN. However, with the growth in the numbers of publishers slowing, it seems that the index is increasingly reflecting the underlying growth in the market, rather than a growth in the adoption of its infrastructure.

Books show less consolidation than journals. The top 10 OA book publishers cover around 45% of book output, while the top 10 OA journal publishers account for around two thirds of OA journal output. This may partly reflect the greater maturity of the journals market. However, it’s likely to be a systemic reflection of how books scale differently.

Users of our OADAT can explore the data in much greater depth, including drilling into the usage of licenses, subjects, and languages.

We will run further analysis of some of these other areas later in the year.

This article is © 2023 Delta Think, Inc. It is published under a Creative Commons Attribution-NonCommercial 4.0 International License. Please do get in touch if you want to use it in other contexts – we’re usually pretty accommodating.

1Methodological note: Our analysis of DOAB metadata returns totals slightly lower than the DOAB’s own headlines, as we filter out book chapters, records with sparsely populated metadata, and have only plotted items until the end of 2022.


Pilot project eliminates author processing charges for all PLOS journals – February 8, 2023

“McMaster University Libraries are partnering with the Public Library of Science (PLOS) in a pilot project to remove financial barriers to publishing research. The two-year project will see the elimination of author/article processing charges (APCs) in all PLOS journals.”

shift+OPEN: An MIT Press initiative to flip subscription journals to open access  February 1, 2023

“The MIT Press welcomes applications for shift+OPEN, our new program designed to flip existing subscription-based journals to a diamond open access publishing model. With generous funding from the Arcadia Fund, shift+OPEN seeks to catalyze needed change in journals publishing, introduce authors to new readerships, and increase the reach of vital scholarship that has previously been locked behind paywalls.”

cOAlition S confirms the end of its financial support for Open Access publishing under transformative arrangements after 2024 – January 26, 2023

“After careful consideration of the outcomes of transformative arrangements, the leadership of cOAlition S reaffirms that, as a principle, its members will no longer financially support these arrangements after 2024.”

JSTOR and university press partners announce Path to Open books pilot – January 17, 2023

“JSTOR, part of the non-profit ITHAKA, and a cohort of leading university presses announced today Path to Open, a program to support the open access publication of new groundbreaking scholarly books that will bring diverse perspectives and research to millions of people.”

Nature drops open-access charges for most of Africa – January 12, 2023

“Publishing giant Nature announced on 9 January that scientists from over 70 countries, of which more than half are in Africa, can now publish research for free in its research journals. The benefit…is designed to help scientists who aren’t well-funded publish open access in the company’s flagship journal Nature, as well as in other Nature research journals, such as Nature Biotechnology.”


January 30, 2023

Mary Ann Liebert, Inc. Launches Robotics Reports — A New Open Access Journal

“Mary Ann Liebert, Inc. announces the launch of Robotics Reports, a new multidisciplinary open access journal devoted to the broad field of robotics. Robotics Reports will provide every author and reader the opportunity to rapidly publish and access the latest technological advances in robotics research.”