English Abstract: We document increased old-age mortality rates among Swedish twin mothers compared to non-twin mothers. Results are based on administrative data on mortality for the years 1990 to 2010. We argue that twins are an unplanned shock to fertility in the cohorts of older women...

English Abstract: Assumptions that are sufficient to identify local average treatment effects (LATEs) generate necessary conditions that allow instrument validity to be refuted. The degree to which instrument validity is violated, however, probably varies across subpopulations. In this paper, we...

German Abstract: Die Verwendung von Instrumental Variablen (IV’s) zur Identifizierung von kausalen Effekten ist weit verbreitet in der empirischen Wirtschaftsforschung. Es ist jedoch fundamental unmöglich deren Validität zu beweisen. Annahmen zur Identifizierung von local average treatment...

English Abstract: We examine heterogeneity in the effect of poor financial circumstances on cognition. Our analysis uses data from an experiment, which randomly assigned low-income individuals to perform a cognitive test before or after payday. On average, and based on traditional subgroup...