Sunday August 29, 2010
Andrew’s off to parliament (holding the swing against Labor to -1.1% 2PP in Fraser). His election is fascinating for those of us with geeky inclinations; I’m intrigued and quietly optimistic as how Andrew’s tenacious commitment to evidence-based, highly-relevant policy research will carry over into his new life.
A straw in the wind, perhaps? The Herald’s economic correspondent, Peter Martin, actually went into some of the inferential details underlying the research on the gun buyback effects, with a reference to “diffs-in-diffs” appearing in his article:
They [Neill and Leigh] used what is known as a difference-in-differences approach, exploiting the fact that some states withdrew guns more quickly than others and examining whether their firearm suicide rates fell faster.
A previous study had found no nationwide effect, noting that firearm suicides began falling before the buyback. However, Dr Neill and Dr Leigh found that states such as Tasmania that withdrew guns quickly had a much bigger decline in firearm suicides than states such as NSW that withdrew more slowly. Whereas the earlier study had found an increase in suicides by other methods, suggesting substitution, Dr Neill’s study found no evidence of substitution within any state.