"Ebook sales increased in adult fiction by 5.3%, now accounting for 20% of total sales, but sales of the format declined in adult nonfiction (down 5.8%) and chi

"Ebook sales increased in adult fiction by 5.3%, now accounting for 20% of total sales, but sales of the format declined in adult nonfiction (down 5.8%) and children’s/young adult (down 1.6%)..." I have been hearing that e-book sales account for around 20% of total book sales since around 2012. Are they sure we're not just talking about noise level up-and-down movement here? A chart to show the long-term trend (or lack of same) would have been useful.