Though most states in the United States require parents to place their children in car seats until they are 6 or 7 years old, Steven Levitt, an American economist says that some studies suggest that seat belts work just as well for children over the age of 2. Car seats are much more effective at preventing fatalities and injuries in kids younger than 2, but some studies suggest that there is virtually no difference in the frequency of fatalities or serious injuries in crashes with children older than 2 when comparing those wearing a lap and shoulder belt with those in a car seat — this in a recent TED talk. Other experts dispute this and strongly recommend that parents continue to use car seats for children up to 40 to 60 lbs (about 18 to 27 kg) or 4 to 7 years of age, as required by law in some places. Booster seats are required in some US states for children up to 60 to 80 lbs (about 27 to 36 kg).
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