Home Office figures show Cleveland Police closed 17,736 theft probes in 2021 – 64% of which had the outcome "investigation complete – no suspect identified".
This was up slightly from 63% in 2020.
A further seven per cent of all theft cases in Cleveland closed with a suspect identified and the victim supporting an investigation but "evidential difficulties prevented further action", while 14% were closed because the victim dropped the case.
Just 11% resulted in a charge or summons – one of the highest rates in the country.
In the force area 58% of cases of stolen motor vehicles were closed with no suspects identified and 89% of reported thefts from a vehicle concluded with no suspect being found.
The cases were among over one million unsolved theft offences in England and Wales, which charity Victim Support said undermines confidence in the justice system.
Jeffrey DeMarco, assistant director at the charity, added: “A million cases unsolved last year seriously undermines victims’ confidence in the criminal justice system.
"Theft is a crime that must always be taken seriously by the police, and work must be undertaken to improve these shockingly low success rates.”
The National Police Chiefs' Council said forces will prioritise cases where there is a realistic prospect of prosecution, and ensure vulnerable victims have the support they need.
A Home Office spokeswomen said 20,000 extra police officers are being recruited to help prevent these crimes.