Bestseller book lists are topped by the likes of Sheryl Sandberg's Lean In, Thomas Piketty's Capital in the Twenty-First Century (which topped the Amazon bestseller lists) and Stephen Hawking's A Brief History of Time (over 10 million copies sold). But how many people actually get all the way through those reads? It turns out, not many.

If you thought the number of people allegedly reading those big doorstops seems suspicious, your doubts may be founded. There are some books that seem better as reputation builders than they are to actually finish. New research from the Wall Street Journal confirms the theory that people aren't really reading all those highfalutin books they claim to be pouring through.

Image Credit: Amazon

For the Wall Street Journal, mathemetician Jordan Ellenberg took a look at some data from Amazon's "Popular Highlights" feature on the Kindle — the Kindle feature that allows readers to highlight passages. Ellenberg decided to look at how spread out the most highlighted passages from the big books of the last few years were, his hypothesis being that books read to their conclusion would contain highlights distributed throughout.

The equation he used, called the Hawking Index (HI) — the name derived from Stephen Hawking's A Brief History of Time, frequently called "the most unread book of all time" — takes the page numbers of each book's top five highlighted passages, averages those page numbers and then divides that number by the number of pages in the book. A 100% HI means the book was finished, and things really devolve from there.

Image Credit: Amazon

What these numbers found is that some books really are read all the way through — like Donna Tartt's Pultizer Prize winning The Goldfinch — while others prove far less engaging. The Great Gatsby may be a tiny little book but the average reader only completed 28.3% of it. Fifty Shades of Grey readers get around a quarter of the way through with an average of 25.9% completion, (and the quotes highlighted tend to be more SFW than not). Lean In managed a disappointing 12.3% even though it previously topped both Amazon and the New York Times bestseller lists. A Brief History of Time, infamous for this sort of trend, managed 6.6%, while the worst culprit was Thomas Piketty's 700-page economy tome Capital in the Twenty-First Century with 2.4% of the book read on average. 

The Wall Street Journal admits that this survey of theirs is not a scientific study — it's more for fun than anything else — but the findings do go to show that there's a big difference between a bestseller and a book that's read.

More importantly, maybe people will now stop making you feel so guilty for not reading economics treatises at the beach. It turns out nobody else is reading them either.