"The Identification Zoo - Meanings of Identification in Econometrics"

Arthur Lewbel, Boston College, forthcoming in JEL:

Well over two dozen different terms for identification appear in the econometrics literature, including set identification, causal identification, local identification, generic identification, weak identification, identification at infinity, and many more. This survey: 1. provides a general framework for characterizing identification concepts, 2. summarizes and compares the zooful of different terms for identification that appear in the literature, and 3. discusses concepts closely related to identification, such as observational equivalence, normalizations, and the differences in identification between structural models and randomization based reduced form (causal) models.

Related: James Heckman and Burton Singer, AER, May 2017:

Abduction is the process of generating and choosing models, hypotheses, and data analyzed in response to surprising findings. All good empirical economists abduct. Explanations usually evolve as studies evolve. The abductive approach challenges economists to step outside the framework of received notions about the "identification problem" that rigidly separates the act of model and hypothesis creation from the act of inference from data. It asks the analyst to engage models and data in an iterative dynamic process, using multiple models and sources of data in a back and forth where both models and data are augmented as learning evolves.

"McHealthcare Deluxe"

Another excellent piece by Kevin Williamson. Money 'graph:

What’s too often lost in the Sturm und Drang of recent Republican efforts to reform the insurance reforms enacted by Democrats in 2009 is this: The Affordable Care Act has not worked as advertised. That is the fundamental fact around which the debate should be organized. The ACA did not result in lower premiums but in the opposite; it did not result in more competitive insurance markets but in the opposite; it did not result in superior health-insurance plans but, at least in many cases, the opposite; it has not resulted in universal coverage. Among the major promises made on behalf of the ACA, only one of any significance has been delivered on: It is the case that more Americans have health insurance today than they did in 2009. But the ACA has underdelivered on that point, too: Only about 16.5 million people — barely 5 percent of the population — gained health coverage from the passage of the ACA through 2016, and the vast majority of those, 81 percent, were new Medicaid beneficiaries.