A new study shows that for men, access to books from a young age corresponds to higher earnings over a lifetime.

… Averaged across nine countries, boys who attended an extra year of school due to changing age requirements eventually returned an additional 9% of income.

But the researchers were surprised to find that, among kids who benefited from an extra year of school, those who grew up with more than 10 non-school books (that is, books they weren’t forced to read) at home eventually doubled that lifetime earning advantage, to 21%. …

Crucially, there was no significant difference between whether participants reported having 50, 100, or 200 books growing up. The key was whether they grew up with any number of books greater than 10.

Source: Economists show that boys who grow up around books earn significantly more money as adults — Quartz