Wagenaar A C, Webster D W, Maybee R G
J Trauma. 1987 Jul;27(7):726-32. doi: 10.1097/00005373-198707000-00006.
Mandatory child restraint laws in 11 states were evaluated for their effect on motor vehicle fatality rates among young children. Data from 1976 through 1983 were analyzed using a monthly time-series design involving 54 months' pre-law and 12 months' post-law data. The 11 states collectively had a mean of 8.8 and a standard deviation of 3.6 fatalities per month among young children. Such small frequency counts resulted in a large proportion of the variation being random. Statistical power analyses found fatality reductions of 20% to 25% following the child restraint laws would be statistically significant. Reductions of such a magnitude were not found for young children. Based on these findings, we recommend that evaluations of highway safety policies focusing on a specific age group within a single state not be limited to analyses of traffic fatalities alone. Studies employing analyses of the larger numbers of crash-induced injuries have identified modest but important casualty reductions not found when analyzing fatalities alone.
