Would you like to hear something that is somehow obvious and totally surprising at the same time? A child who grows up in a home with at least 80 books will have significantly greater levels of literacy, numeracy, and technology skills in adulthood.

In fact, results are so powerful that literacy levels in children with home libraries who never go to college have similar literacy levels to those growing up with a small home library but advanced degrees (both average literacy).

As the library climbs above 80 books, those effects become even more remarkable, but according to some research, the advantages essentially level off at about 350 books. Others argue that they have seen increased positive outcomes in homes with 500 books or more, although a goal of a few hundred books seems to be a safe bet. In fact, a home library of just 100 books added an extra 1.5 years to a child’s grade-level reading performance.

Is it enough to just own the books? Researchers aren’t yet sure, although longitudinal studies have consistently demonstrated that books in the home have a huge effect on literacy that persists into adulthood. One hypothesis is that this might be more related to a “book-oriented socialization,” or the fact that a family owning a lot of books may hold education and learning in esteem. For example, a child that sees a parent reading might emulate that behavior. Another thought is that books also simply help teach these skills and competencies.

Despite not being able to state with certainty why the books in the home matter—studies have consistently demonstrated that this single factor can overcome almost any other factors that tend to affect literacy levels including: economic situation, nationality, and parent level of education.

While the discussion swirls largely around home libraries containing books people ‘own,’ there’s certainly an argument that library books can be a supplement and possibly even help replace ‘owned’ books. When people sign up for library cards they frequently ask: “how many items can I have at one time?” Most are shocked to learn that the limits are quite high: 100 items in fact. We generally respond by saying, “as many as you think you can keep track of….” You can certainly create a bookish and literacy-positive environment, giving children educational and skill advantages, with a wallet that contains no money but possesses a library card.