According to the Census Bureau, 7.8 million children lived with at least one grandparent in 2009, a 64 percent increase since 1991. The data was collected in 2009 as part of the household relationship module of the Survey of Income and Program Participation. The Survey of Income and Program Participation is a longitudinal panel survey of demographic information, income, labor force characteristics, and program participation in the United States with supplemental topics on child well-being, child care, and household relationships. Census demographers note that the living arrangements of children in the United States is an important indicator of child well-being.