Income level is presented in quartiles. The first quartile (Q1) represents 25% of families with the lowest incomes; the second quartile (Q2) represents the 25% of families with income below the median value but above the first quartile; the third quartile (Q3), represents the 25% of families with income higher than the median value but lower than the forth quartile, and the fourth quartile (Q4) represents the 25% of families with the highest incomes. The weekly care hours are grouped into 3 categories: 0 hours; from 1 to 29 hours; 30 or more hours. Formal care refers to organised structures with qualified staff, whether at pre-school centres or at a registered family-type structure.