This change is the product of three separate trends. Between 1996 and 2000, the share of children living with a never-married parent rose (from percent to percent), but this increase was outweighed by a drop (from percent to percent) in the share living with a divorced parent. The share living with a widowed parent remained constant, at percent of all children. In numerical terms, the number of children living with never-married parents increased by 400,000, but that was offset by a decline of 1 million kids living with divorced parents. The combination of these trends resulted in a smaller share of kids living with a single parent by 2000.
In nearly all countries, students living in single-parent families have lower achievement on average than students living in two-parent families (see Figure 2a). In the United States, the average raw achievement difference in math between students living in two-parent families and students living in single-parent families is 27 points, or roughly one grade level. The United States is one of six countries with achievement differences larger than 25 points. Belgium has the largest disparity in math achievement by family structure, at 35 points, followed by the Netherlands (29), and Poland, Japan, and the United Kingdom (27 to 28). On average across the 28 countries, students living in single-parent families score 18 points lower than students living in two-parent families.