Analyses of foster home utilization and length of service were based on the span of time during which children were placed in the foster home, rather than licensing dates. These analyses were limited to homes in which the date of the initial license was known to occur after the dates for which child placement records were available to ensure that all placements in the home could be identified. This restriction created entry cohorts of foster parents whose entire foster parenting career could be examined.
Episodes of active foster parenting were defined as the number of days between the beginning of the first placement of a child in that home and the exit date of the last child placed in the home or the end of the study period. A gap of more than 90 days without a placement in the home signaled the start of a second episode of active foster parenting. Across the three states, between 74 and 87 percent of homes had only one episode of active foster parenting during the years studied. Among homes that were without placements for at least 90 days, only a minority were likely to subsequently resume foster parenting. All analyses of foster home utilization and foster parent length of service were based on the first episode of foster parenting.
Analysts created two measures to describe the intensity of foster care provision: occupancy rate and new placement rate. The occupancy rate was defined as the number of placement days for all children in the home divided by the number of days of foster parenting. It is equivalent to the average number of children in the home on a hypothetical day. Because episodes of active foster parenting may have included one or more periods of up to 90 days with no placements in the home, these occupancy rates are lower than those reported based on the average number of children in homes currently providing foster care.
To describe variations in the extent to which foster parents dealt with different children over time, the new placement rate was calculated as the number of new placements in a home, divided by the number of days in the first episode of foster parenting. The resulting figure was multiplied by 365 to create an annualized rate. A home with six new placements during 2 years of active foster parenting would have a new placement rate of 3; whereas a home with six new placements during 6 months of foster parenting would have a new placement rate of 12. Note that this formula can yield very high rates for foster homes that care for children for very short periods of time. A home that provided care to four children for 2 days, and had no other foster placements, would have an annualized rate of 4 ÷ 2 × 365, or 730. Very high rates for some groups are likely to represent short time in foster parenting, rather than homes that care for hundreds of children annually.