Child support payments vary wildly from state to state

• The Northeast has highest child support payments, while Rocky Mountain states are the lowest.
• Child support is $100 more in states that don't consider a mother's income.
• Mississippi, North Dakota and Texas still don't compute mothers' income into their calculations.

If you're a divorced mother residing in Massachusetts with children 7- and 10-years old, don't move to Vermont. Your child support payments could be cut in half.

A study conducted by Custody X Change, which offers a web app to help parents with custody agreements, shows that moving the 28 miles from North Adams, Massachusetts, to Bennington, Vermont, could lessen your child support payments from $1,187 to $519 per month. And relocating several hundred miles south to Virginia could reduce that support payment by almost two-thirds.

As any divorced parent knows, child custody and support can be extremely arbitrary. Although guidelines exist, federal law allows each state to set its own rules, and quite often states measure support using a very different yardstick. Judges also have discretion. Another big factor in each equation for ultimately deciding who pays what to whom: which parent has custody and for how much time? Those payments can vary by more than $700 a month, according to Custody X Change.

"Common sense is that child support should be tied to the cost of living," said Melissa Avery, chair of the American Bar Association's family law section. "But every state handles it differently. Legislators hear from lobbyists." She warned: "If you're moving to another state, get some legal advice."

The Custody X Change study is based on hypothetical calculations: a split couple with two children, ages 7 and 10, in which the father earns $55,000 and the mother makes $45,000. Based on a recent Pew study, that total income seems a bit high in comparison to Census data from 2015, which showed the average two-earner family brought home about $56,000. It also takes into account that the mother spends more of her time, energy and money on child care than the "noncustodial" father, 65% vs. 35%, respectively.

Why child support varies so much

The varying yardsticks create some surprising results. For example, New Jersey ranks 47th in child support payments, even though it's one of the most expensive states in which to live. Massachusetts is first, and Nevada second. According to the study, the Northeast region ranks higher, while Rocky Mountain states rate the lowest.

Several reasons account for why child support doesn't always align with either politics or the cost of living. One big factor: whether the state has caught up with the reality of working women. States are supposed to review guidelines every four years, but three -- Mississippi, North Dakota and Texas -- still don't compute mothers' income into their calculations. This causes the father's theoretical support payment to be $100 higher, according to the study.

Another factor is that states don't want to set support payments so high that the noncustodial parent can't afford to pay them. A grim calculus can lead some parents to abandon a child if they believe they're paying too much. That's especially likely when the parent is self-employed, said the ABA's Avery.

Many other variables come into play such as remarriage, custodial children outside the relationship, health insurance, public assistance and alimony, which is less common now than before.