“The average child growing up in a middle-class family has been exposed to 1,000 to 1,700 hours of one-on-one picture book reading. The average child growing up in a less economically stable family, in contrast, has only been exposed to 25 hours of one-on-one reading.” (J. McQuillan, The literacy crisis: False claims, real solutions. Portsmouth, NH: Heinemann, 1998.)
“Because low-income children have limited access to books, they also likely miss out on the stimulating parent-child interactions around books and stories, in particular, the read-aloud. and without the read-aloud, children are deprived of the opportunity to learn about their world, acquire more sophisticated vocabulary beyond their everyday language, and understand how decontextualized language works, which is the beginning of abstracting information from print.”
From Make Every Student Count
Family and Community Engagement 2013 Research Compendium
Read the “Access to Books” section of the report (PDF)

(This is a compendium of research produced by many scholars in many circumstances; however, note that FACE is sponsored by Scholastic Books, an organization with an obvious interest in proliferation of books.)