Raising the minimum age for purchasing cigarettes from 16 to 18 in England associated with lower youth smoking

I have been a skeptic about the value of minimum purchase laws as strategy for reducing youth smoking, but a study we just published from England showed that increasing the minimum purchase age from 16 to 18 was associated with a drop in smoking among 11-15 year olds, even after taking into account the existing downward trend.  The effects were similar across socio-economic groups. We did not have the data to evaluate whether these effects persisted as kids got older (i.e., Did the law prevent initiation or just delay it?).  It will take a few years to answer that question because we have to wait for the kids to get older. In any event, raising the minimum age to 18 was a good thing.