Lars P. Syll

Sex and the problem with interventionist definitions of causation We suggest that “causation” is not univocal. There is a counterfactual/interventionist notion of causation—of use when one is designing a public policy to intervene and solve a problem—and an historical, or more exactly, etiological notion—often of use when one is identifying a problem to solve … Consider sex: Susan did not get the job she applied for because the prejudiced employer took her...

Was the Swedish corona strategy a success? .[embedded content] Any scientific discussion about whether all or some versions of treatment lead to the same causal conclusion rests, again, on expert consensus and judgement. Because experts are fallible, the best we can do is to make these discussions—and our assumptions—as transparent as possible, so that others can directly challenge our arguments. Miguel Hernán

Which causal inference method is the best one? .[embedded content]

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Graphical causal models and collider bias Why would two independent variables suddenly become dependent when we condition on their common effect? To answer this question, we return again to the definition of conditioning as filtering by the value of the conditioning variable. When we condition on Z, we limit our comparisons to cases in which Z takes the same value. But remember that Z depends, for its value, on X and Y. So, when comparing cases where Z...

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Hunting for causes (wonkish) There are three fundamental differences between statistical and causal assumptions. First, statistical assumptions, even untested, are testable in principle, given sufficiently large sample and sufficiently fine measurements. Causal assumptions, in contrast, cannot be verified even in principle, unless one resorts to experimental control. This difference is especially accentuated in Bayesian analysis. Though the priors that...

Natural experiments in economics Thad Dunning’s book Natural Experiments in the Social Sciences (CUP 2012) is a very useful guide for economists interested in research methodology in general and natural experiments in specific. Dunning argues that since random or as-if random assignment in natural experiments obviates the need for controlling potential confounders, this kind of “simple and transparent” design-based research method is preferable to more...

The tools economists use In their quest for statistical “identification” of a causal effect, economists often have to resort to techniques that answer either a narrower or a somewhat different version of the question that motivated the research. Results from randomized social experiments carried out in particular regions of, say, India or Kenya may not apply to other regions or countries. A research design exploiting variation across space may not yield the...