A 2016 systematic review of CI for people with unilateral hearing loss (UHL) found that of the studies conducted and published, none were randomized, only one evaluated a control group, and no study was blinded. After eliminating multiple uses of the same subjects, the authors found that 137 people with UHL had received a CI. While acknowledging the weakness of the data, the authors found that CI in people with UHL improves sound localization compared with other treatments in people who lost hearing after they learned to speak; in the one study that examined this, CI did improve sound localization in people with UHL who lost hearing before learning to speak. It appeared to improve speech perception and to reduce tinnitus.