An estimate of how family size and type affects budget has been developed by the US Bureau of Labor Statistics. You can use the table below to consider cost of living changes along a typical family life cycle. The normalization basis for this table is a family of four (two adults and two children). All other budget entries represent the normalized funding required for the specified family to maintain an equivalent lifestyle to the base family. For a single young person prior to marriage the cost of living is 36% that of our normalized family of four. The cost of living for a married couple increases to 60% of the normalization base. When one child is added, the family budget is at 82% of the base. A second child puts the family at base budget level. A third child places the couple at 111.6% the cost of a family of four. For cases not shown in the table, the equivalence family budget can be roughly approximated using the expression
E = ((A+pK)^F)/2.751
where A is the number of adults in the family, K is the number of children, p=0.92 and F=0.75.
Equivalence Scale used by US Bureau of Labor Statistics. The equivalence scale is used to adjust financial thresholds for differences in household size and composition.
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FAMILY TYPE . . . . . . BLS NORMALIZED FAMILY BUDGET
Single Adult - - - - - - - - - - - - 0.360
Two Adults- - - - - - - - - - - - - 0.600
Two Adults, One Child- - - - - 1.000
Two Adults, Three Children- - 1.116
One Adult, One Child- - - - - - 0.570
One Adult, Two Children- - - - 0.760