Another methodological improvement was made starting with the 2009 eligibility estimates that affected the number of children eligible under federal parameters. This change included the treatment of income of assistance-unit members other than the spouse, head, and eligible children. Before 2009 older siblings of the children were included in the family count but their incomes were not included. Starting in 2009, the estimates include the older children in the family count and their incomes are added to their parents when determining family income. For purposes of these estimates the definition of the assistance unit is based on the subfamily, as defined by the Census Bureau, and family members outside of the subfamily unit are not included in the benefit determination formulas.