Three Formulas, One Country: How US Child Support Calculations Diverge by State

Findings

Income Shares dominates at 43 of 51 jurisdictions

PlainChildSupport's states table lists 43 jurisdictions with formula_type column set to Income Shares, covering 50 states plus DC, including Illinois. Each row stores base percentages, income cap values, and URLs to official state calculators. Income Shares model combines both parents' incomes, then pulls obligation amounts from state-specific schedule tables. National Conference of State Legislatures, Child Support Guidelines by State Developers access these via joins on state_fips in child support calculators. DC row shows median household income at $90,842 with income cap above that level. Maryland row records $90,203 median household income, also Income Shares with cap exceeding median. New Jersey row lists $89,703 median household income under same formula_type. US Census Bureau, ACS 2022, Table B19013 (Median Household Income)

Low-median-income states apply Income Shares alongside self-support floors in states table. West Virginia row holds $48,037 median household income. Arkansas row shows $48,952 median household income. States table formula_type column confirms Income Shares for both. US Census Bureau, ACS 2022, Table B19013 (Median Household Income) Nine jurisdictions deliver verified official calculators replicated in PlainChildSupport: California, Florida, Georgia, Michigan, New York, North Carolina, Ohio, Pennsylvania (all Income Shares), plus Texas from the Percentage of Income model. All nine embed parenting-time adjustment at 40% overnights, or 146 nights per year. Formulas-explained guide details Income Shares schedule lookups.

Enforcement data ties to Income Shares states. Iowa collects 68.4% of assessed support. North Dakota reaches 67.5% collections. Minnesota hits 67.2% in FY2023 data. Office of Child Support Enforcement, FY2023 Preliminary Report States table links to enforcement agency calculators for these jurisdictions. High collection rates pair with Income Shares formula_type in 43 rows. West Virginia self-support floor compresses obligations at $48,037 median household income level.

Percentage of Income: five states span 14% to 20%

States table marks 5 jurisdictions with formula_type as Percentage of Income: Texas at 20%, Nevada at 18%, Wisconsin at 17%, North Dakota at 14.35%, Mississippi at 14%. National Conference of State Legislatures, Child Support Guidelines by State Base percentages column stores these rates for one child. Spread between lowest Mississippi 14% and highest Texas at the one-fifth-of-income rate spans 6 percentage points. Non-custodial income alone drives obligations, unlike Income Shares combined totals. Texas state page replicates official calculator at the flat rate.

Texas Percentage of Income applies the flat one-fifth rate to non-custodial gross income, diverging fundamentally from Income Shares math that combines both parents' incomes into a schedule lookup. Texas state page holds a verified calculator matching the state enforcement tool, the only Percentage of Income state among the nine verified jurisdictions. North Dakota row lists 14.35% base with 67.5% collections rate. Mississippi row shows 14% base percentages and 49.3% collections. Office of Child Support Enforcement, FY2023 Preliminary Report States table income cap column varies across these 5 rows.

Parenting-time adjustments activate at 40% overnights in verified Percentage states. Texas follows the 40% overnights threshold, or 146 nights per year, same as the Income Shares calculator states. Nevada 18% base rate row links to state agency guidelines. Wisconsin 17% stores in base percentages column without a verified calculator. North Dakota's 14.35% is likewise unverified in this dataset. Five rows total under this formula_type enable direct rate comparisons. State child support enforcement agencies, official calculator URLs

Melson's 3 holdouts, Delaware, Hawaii, and Montana

Three jurisdictions claim formula_type Melson in states table: Delaware, Hawaii, Montana. National Conference of State Legislatures, Child Support Guidelines by State Melson subtracts self-support reserve from each parent's income before percentage application. Delaware row links to official guidelines via states table URL column. Delaware state page documents reserve test. Hawaii row records Melson parameters in base percentages column. Montana completes the 3 rows with same formula_type.

States table self-support reserve values appear in Melson rows for Delaware, Hawaii, Montana. No Melson states join the 9 verified calculators group. Delaware Melson applies after reserve subtraction, differing from Percentage flat rates. Hawaii guidelines URL points to enforcement agency tool. Montana row holds income cap alongside Melson details. State child support enforcement agencies, official calculator URLs Total Melson count stays at 3 across 51 jurisdictions.

Enforcement collections provide context for Melson states. Mississippi 49.3% rate contrasts North Dakota 67.5%, though different formula_type. Delaware self-support reserve aligns with low-income compression patterns like West Virginia $48,037 median. Hawaii and Montana rows enable Melson-specific queries via formula_type filter. Office of Child Support Enforcement, FY2023 Preliminary Report States table page lists all 51 with Melson isolated.

States table captures formula_type distribution across 51 jurisdictions: 43 Income Shares rows, 5 Percentage of Income rows with 14% to 20% base rates spanning 6 points, 3 Melson rows. High-income DC $90,842, Maryland $90,203, New Jersey $89,703 use Income Shares caps above medians; low-income West Virginia $48,037, Arkansas $48,952 compress via floors. Verified calculators in 9 states embed 40% overnights threshold, including Texas at the Percentage of Income one-fifth base. Collections range from Iowa 68.4% to Mississippi 49.3%. US Census Bureau, ACS 2022, Table B19013; Office of Child Support Enforcement, FY2023 Preliminary Report