1. International Publishers Association (IPA): According to the IPA, an estimated 1.5 million new book titles were published worldwide in 2020. This includes books published by traditional publishers and self-published books.
2. UNESCO Institute of Statistics (UIS): The UIS estimated that around 2.3 million books were published globally in 2018. This estimate is based on data collected from 114 countries and includes books published in all formats (print, electronic, and audiobooks).
3. Bowker: Bowker, a provider of bibliographic information, reported that over 1.7 million books were published in the United States alone in 2019. This includes both traditionally published books and self-published books.
Please note that these estimates may vary due to different definitions of what constitutes a "book," variations in data collection methods, and the exclusion or inclusion of certain categories of books (such as academic dissertations or government publications). Additionally, the COVID-19 pandemic may have affected book publishing in 2020 and 2021, so these estimates may not accurately reflect the number of books published in those years.