Three formulas: how state child support diverges

43 of 51 US jurisdictions use Income Shares, 5 use Percentage of Income, and 3 use the Melson self-support-reserve model, a mechanical split that produces radically different outcomes at identical incomes.

Research period:

Research Question

Across the 51 US jurisdictions (50 states + DC), how are child support formulas distributed, and how do the three mechanical models produce different obligations at the same income?

Methodology

We queried PlainChildSupport's states table, which codifies each jurisdiction's formula type, base percentages, income cap, and whether the state publishes an official verifiable calculator. We grouped the 51 rows by formula_type and counted the distribution. For the 5 Percentage of Income states, we sorted by base_pct_1child to show the rate spread. Every statutory percentage is pulled from the state's official guidelines page linked in the official_calculator_url or guidelines_url column. Counts on this page are rendered from the live table, not typed constants.

Findings

Income Shares dominates at 43 of 51 jurisdictions

PlainChildSupport's states table lists 43 jurisdictions with formula_type set to Income Shares (50 states plus DC). Each row stores base percentages, income caps, and URLs to official state calculators or guideline documents. The Income Shares model combines both parents' incomes, then pulls the obligation from a state-specific schedule. National Conference of State Legislatures, Child Support Guidelines by State High-median Income Shares rows include District of Columbia ($90,842), Maryland ($90,203), New Jersey ($89,703). US Census Bureau, ACS 2022, Table B19013 (Median Household Income)

Low-median Income Shares rows include West Virginia ($48,037) and Arkansas ($48,952), where self-support floors matter more relative to the schedule. US Census Bureau, ACS 2022, Table B19013 10 jurisdictions currently carry a verified official calculator flag in the same table (has_calculator=1), including Texas from the Percentage of Income model. Formulas-explained guide details Income Shares schedule lookups.

Percentage of Income: 5 states span 14% to 20%

States table marks 5 jurisdictions as Percentage of Income: Texas (20%), Nevada (18%), Wisconsin (17%), North Dakota (14.35%), Mississippi (14%) (a 6-point spread). National Conference of State Legislatures, Child Support Guidelines by State Non-custodial income alone drives the obligation, unlike Income Shares combined totals. Texas state page replicates the official flat-rate calculator.

Texas sits at the high end of that Percentage band; Mississippi anchors the low end. Parenting-time credits still matter inside the model (Texas triggers around 40% overnights), but the starting rate is a single statutory percentage rather than a schedule lookup. State child support enforcement agencies, official calculator URLs

Melson's 3 holdouts: Delaware, Hawaii, Montana

Three jurisdictions claim formula_type Melson: Delaware, Hawaii, Montana. National Conference of State Legislatures, Child Support Guidelines by State Melson subtracts a self-support reserve from each parent's income before applying the support share. Delaware state page documents the reserve test. No Melson state currently sits in the 10-jurisdiction verified-calculator set.

Across all 51 rows the live distribution is 43 / 5 / 3 (Income Shares / Percentage of Income / Melson). That is the same population the homepage formula cards and the charts below render from. NCSL Child Support Guidelines; PlainChildSupport states table

What this analysis cannot tell us

The base percentage in a Percentage of Income state applies before deductions and credits; actual take-home obligations differ because of self-support reserves, parenting-time adjustments, and health-insurance splits. Income Shares states use obligation tables that are not reducible to a single percentage; the 43-jurisdiction count treats the formula as a model class, not a single number. Melson states apply a self-support reserve before the support share, so Delaware is not comparable line-for-line to Texas's flat share of capped gross income. PlainChildSupport does not model tax treatment. This page does not cite per-state collection rates: the federal preliminary report publishes no honest per-state column for that metric in our dataset.

Related data

Sources

Formula type, adoption count across states

Income Shares43Percentage of Income5Melson Formula3

Percentage of Income base rate, 1-child (all 5 states)

Texas20Nevada18Wisconsin17North Dakota14.35Mississippi14

Every figure on PlainChildSupport is rendered directly from official state guidelines and federal enforcement data, no number is typed in by an editor. This page draws directly on official state guidelines and federal enforcement data, no figure is typed in by an editor. See our editorial standards & corrections policy, the methodology behind these numbers, or report a data error.

PlainChildSupport publishes state guideline data and federal enforcement statistics for informational purposes only. It is not legal or financial advice, a calculator result is not an order, and every state allows deviations a court decides case by case, so confirm any figure with the state child-support agency or an attorney before you rely on it. Appropriate use.