The US federal government collects much data about child support and its enforcement.  Over the past 50 years there have been many changes in the enforcement process.  (See history 1950-2012 and 2013 update.).

In addition to this description you can see the changes in the demographics of the participants over time.  Below is a summary of this 2013 report.

The national Census Bureau data show that in 2011, 14.4 million parents had custody of children under age 21 while the other parent lived elsewhere, and the aggregate amount of child support received was $23.6 billion. In 2011, 82% of custodial parents were mothers. Of all custodial parents, 50% were white, 25% were black, 21% were Hispanic, 18% were married, 33% were divorced, 35% were never married, 15% did not have a high school diploma, 17% had at least a bachelor’s degree, 50% worked full-time year-round, 29% had family income below poverty, and 39% received some type of public assistance. In 2011, only 2.7 million (38%) of the nearly 7.1 million custodial parents with child support orders actually received the full amount of child support that was owed to them. The average yearly child support payment received by custodial parents with payments was $5,160 for mothers and $4,433 for fathers. These full or partial payments represented 17% of the custodial mothers’ total yearly income and 11% of the custodial fathers’. Compared to 1993 Census data, less child support was received by custodial parents in 2011 ($23.9 billion in 1993 versus $23.6 billion in 2011; in 2011 dollars). However, a higher percentage of those owed child support actually received all that they were due (36.9% in 1993 versus 43.4% in 2011).