Drink, death, and driving: Do blood alcohol content limit reductions improve road safety?
利用苏格兰降低法定血液酒精含量上限而英国其他地区不变的自然实验，采用双重差分法发现该政策对交通事故率和死亡率均无显著影响。
This study exploits a natural experiment in Scotland where the legal blood alcohol content (BAC) limit was reduced from 0.8 to 0.5 mg per 100 ml of blood while staying constant in all other parts of the United Kingdom. Using a difference-in-differences design, we find that this change in the BAC level had no impact on either traffic accident or fatality rates.