There are many things one may take issue with in Marie Kondo’s mega-best-selling The Life-Changing Magic of Tidying Up, but for a certain sort of person, one particular piece of advice she gives is unthinkable: Throw away your books, she says. Get rid of as many as you possibly can, both the ones you’ve read and the ones you haven’t (and know you never will). For your very favorites, she allows, you may rip out the best parts and keep only those pages.
This is impossible advice to follow for bookworms, whose preferred home environments look something like beloved used-book stores. And there is now, Quartz reports, a bit of empirical evidence about the lasting benefits of keeping stacks of books lying around, at least in childhood — kids who grow up around books end up being more successful. In a study of nine European countries, a team of economists from Italy found that boys who had access to non-school-related books grew up to make 9 percent more, on average, than boys who did not have many non-textbooks around. (Alas, this data set focused only on the guys.)
Writer Thu-Huong Ha breaks down the study methodology:
The researchers based their models on data collected from men between ages 60 and 96 from Austria, Belgium, the Czech Republic, Denmark, France, Germany, Italy, the Netherlands, and Sweden, part of a massive ongoing survey of Europeans. They compared whether the men grew up in rural or urban environments, the years they were in school, roughly how many books they had in their houses at age 10, and their income across their lives.
According to the study, which was published in The Economic Journal, the magic number of non-schoolbooks appeared to be ten. “Crucially, there was no significant difference between whether participants reported having 50, 100, or 200 books growing up,” Ha explains. “The key was whether they grew up with any number of books greater than ten.”
This study captured data from in the pre-internet era, so it’s not clear what this may mean for children growing up today. And it’s true that it may not be the books themselves that created this association, or not exactly, anyway. A house with books is likely a house that values education; it may also be a signal of higher socioeconomic status.
But in recent years, psychological science has found that reading fiction increases empathy; one 2014 study on the Harry Potter series in particular found that kids who read about magic and Muggles were more likely to have positive feelings about people who were different from them. Perhaps the emotional intelligence that kids gain from reading helps set them up for success later in life. In sum: Books are great! Keep ‘em around.