Seat designs must have both the strength to retain an occupant in a high-severity rear impact and the energy-absorbing characteristics necessary to limit injuries in more frequent low-severity impacts. This study evaluated the relative performance of modern seats in high-severity rear impacts while also assessing if a necessary trade-off existed in occupant injury protection in low-severity rear impacts. Twenty-six high-severity simulated rear-impact tests were conducted on seats in the modern fleet. The results from these tests were analyzed for relationships with metrics from previously conducted low-severity simulated rear impacts and with insurance injury claim data. Additional analysis was done for low-severity test metrics and insurance injury claim data. The majority of seats tested had adequate occupant retention for a 78 kg occupant at the tested severity. Better occupant-retention metrics in the high-severity test were not linked with increases in low-severity injury test metrics or real-world injury claim rates, indicating that some seats in the modern fleet provide occupant retention at high severities and whiplash injury protection at low severities. Further, results showed that some metrics from the high-severity test had better correlations with insurance injury claim rates than any low-severity metrics and that a metric not currently used for whiplash evaluation, longitudinal pelvis displacement, showed enough potential for predicting injury claim rate that it warrants further research.