ement error in the driver injury report and dr iver seat belt status, especially since they are recorded by the same offi cer. Depending on whether and how this measurement error is related to the officer’s reporting of restraint type s, it can bias the estimation in either direction. It is worth noting that omitting the driver injury measures does not systematically affect the estimates on restraint types. 8 Using a lap-and-shoulder belt increases these injuries by .0015 relative to child safety seats, compared to an increase of .0265 for riding unrestrained. The ratio of the coefficients on lap-and-shoulder belts and no restraint is approximately .06 (.0015/.0265), implying that lap-and-shoulder belts provide 94 percent of the benefits of child safety seats (1-.06=.94). 9
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