* No Official, Centralized Tracker: Unlike some books with a single publisher, the Hunger Games series has been published by Scholastic (US) and Scholastic UK. These separate publishers might have different sales figures, and there's no official, combined total released.
* Digital Sales: The rise of ebooks and audiobooks makes tracking exact physical copies sold difficult. It's also worth noting that many people likely read the series through libraries or borrowed copies, further adding to the difficulty of tracking.
* Global Sales: Sales figures are reported by country, and global figures are not always publicly available.
However, we can say with certainty that the Hunger Games trilogy has been a phenomenal success, selling millions of copies worldwide. It has also been translated into many languages, further adding to its reach.
The series' popularity is undeniable, but the exact number of copies sold is a figure that remains elusive.