Rib fractures may be dismissed as clinically insignificant, or of secondary importance in a patient presenting with other serious injuries, especially if the patient is young. This study assesses the effect of concomitant rib injuries on fatality risk following a car crash, and compares the effect as a function of patient age. The National Trauma Databank was sampled to identify 181,331 adults that were in motor vehicle crashes and had complete data available. Characteristics among several populations were compared, including the association between rib fractures and fatality risk in two age groups (18 to 45 years old and over 64 years old). Descriptive statistics were compiled to contrast the injury patterns and outcomes. Propensity scores were then generated using logistic regression, where the "treatment group" was those patients with rib fractures of at least an abbreviated injury scale (AIS) 3. Covariates for generating the propensity score included gender and the presence or absence of AIS 3, 4 or greater injuries to the head, abdomen or pelvis. Matching was performed using calipers on the propensity scores for all patients within the two age groups. Odds ratios for the outcome death were calculated for the matched datasets and compared between the two age groups. The probability that an adult with automotive blunt trauma had a rib injury as the maximum AIS (MAIS) increased significantly (p<0.001) with age. Furthermore, the probability of the patient having an MAIS defined by rib fractures increased significantly with age for adults who died with a thoracic MAIS: from 30.4% at age 21 to 51.3% at age 65. Rib fractures defined the MAIS for 55.9% of all patients over age 60 who died with a thoracic MAIS. In other words, over 55% of patients over 60 who died of a chest injury had no injury worse than rib injuries. The odds ratio for death for younger patients (aged 18-45) was 1.4 (95% CI 1.3-1.6) if rib fractures of at least AIS 3 or greater were present. For older patients (over 64 years) the odds ratio was 2.5 (95% CI 2.3-2.8). In other words, regardless of the presence or absence of concomitant trauma, crash-injured patients with rib fractures of at least AIS 3 have a significantly increased risk of in-hospital mortality, and of two patients having similar non-rib trauma, one with AIS 3+ rib fractures has a substantially higher expected risk of death than one without. This effect is more dramatic for older patients.