The investigative study, conducted by students at the Medill School of Journalism at Northwestern University in Evanston, Ill., found some states and counties have far higher rates of prosecution than others.
Nebraska has the highest rate of shaken-baby cases, the group found, followed by Utah, Oklahoma, Wisconsin and Ohio. Some jurisdictions within those states have much higher rates.
Experts said identifying places with higher rates is only a first step.
"A higher rate, for instance, could mean authorities are being effective in catching the cases when they occur, or it could mean there is a high number of caregivers who are violently shaking infants," the report said. "Bias in the media and misdiagnoses may also be impacting the number of reported accusations."
In recent years, a number of people convicted of killing or harming infants by shaking them hard have been released. Judges determined the damage could have had other causes, including congenital problems.
The report said that in some counties aggressive prosecutors pursue every case that might be shaken baby syndrome. In others, the opinions of doctors have had a major influence.