PISA group definitions by books in the home

Number of books in home
2000 2003 and after
Group 0 0
Group 1 110 0–10
Group 2 11–50 11–25
Group 3 51–100 26–100
Group 4 101–250 101–200
Group 5 251–500 201–500
Group 6 >500 >500

Source: OECD Program for International Student Assessment (PISA) 2000, 2003, 2006, and 2009 databases

View the underlying data on epi.org.