In recent decades, the provision of early childhood education and care (ECEC) has risen up the policy agenda right across the globe. One central driving force has been the increasing labour force participation of women, which has created a growing demand for childcare services for preschool age children. Governments have encouraged and subsidised these services for a number of reasons. Concerns about child poverty have figured prominently in countries such as the UK, while the need to tackle social exclusion among immigrant groups has been a factor in many continental European countries. Demographic change has also been important. Rising rates of lone parenthood have created fiscal pressure in countries where the state has traditionally stepped in in the absence of a male breadwinner. In some countries, for example Germany, the policy goal of facilitating work–family balance has been coupled with that of promoting fertility rates.

At the same time, there has been growing interest in the value of early education from a child development perspective. Research has increasingly underlined the importance of what happens in a child's early years for their later life chances (for a review, see Almond and Currie, 2011). Evidence from a wide range of countries indicates that children who have had exposure to preschool education do better at school, and that the benefits are long lasting (Heckman et al, 2010; Ruhm and Waldfogel, 2012).

Two points in particular emerge clearly from the research into the impact of ECEC. The first is the importance of quality: children stand to gain much more where the quality of provision is higher (Shonkoff and Phillips, 2000; Blau, 2001; Baker and Milligan, 2008; Sylva et al, 2011). What is understood by quality can vary between (and within) countries but broadly, children appear to do best in settings in which adults interact with children in a responsive, sensitive and stimulating way. If care is low quality the expected benefits do not materialise, and some provision may even be damaging to children's prospects. Thus, while at its best childcare is far more than just somewhere to park children while parents are working, not all settings will promote children's cognitive, social and emotional development: what happens in a setting is crucial.

The second point is that ECEC appears to make the most difference to children from disadvantaged backgrounds (Ruhm and Waldfogel, 2012). There are a number of possible reasons for this.