arXiv subjects

Senan Hogan-Hennessy

Publications and source records attributed to Senan Hogan-Hennessy.

3 recordsLinked to original sources

arXiv2026

The Direct and Indirect Effects of Genetics and Education

Genes associated with educational attainment causally improve labour market income, but the economic mechanism behind this relationship is not clear. Using quasi-random variation in genetic inheritance across siblings in the UK Biobank, I estimate the causal effect of the Education PolyGenic Index (Ed PGI) on education and income. A one standard deviation increase in the Ed PGI raises completed education by 0.5 years and later-life income by around 5 percent (replicating the main estimates in Carvalho 2025). I then decompose this total genetic income effect into an indirect channel operating through education years and a residual direct effect, using a causal mediation framework. Unlike structural model-based decompositions, this approach is design-based; one remaining source of uncertainty (the causal return to an extra year of education) is handled transparently through a sensitivity analysis. At correlational education returns of around 6 percent, 65 to 75 percent of the total genetic income effect operates through the years of education channel. Quasi-experimental estimates from the economics literature for Britain imply higher returns to education, suggesting that the mediated share is larger and that the majority of the Ed PGI's income effect operates through completed years of education.

econ.GN↗

arXiv2026

Causal Mediation in Natural Experiments

Natural experiments are a cornerstone of applied economics, providing settings for estimating causal effects with a compelling argument for treatment randomisation, but give little indication of the mechanisms behind causal effects. Causal Mediation (CM) is a framework for sufficiently identifying a mechanism behind the treatment effect, decomposing it into an indirect effect channel through a mediator mechanism and a remaining direct effect. By contrast, a suggestive analysis of mechanisms gives necessary but not sufficient evidence. Conventional CM methods require that the relevant mediator mechanism is as-good-as-randomly assigned; when people choose the mediator based on costs and benefits (whether to visit a doctor, to attend university, etc.), this assumption fails and conventional CM analyses are at risk of bias. I propose an alternative strategy that delivers unbiased estimates of CM effects despite unobserved selection, using instrumental variation in mediator take-up costs. The method identifies CM effects via the marginal effect of the mediator, with parametric or semi-parametric estimation that is simple to implement in two stages. Applying these methods to the Oregon Health Insurance Experiment reveals a substantial portion of the Medicaid lottery's effect on subjective health and well-being flows through increased healthcare usage -- an effect that a conventional CM analysis would mistake. This approach gives applied researchers an alternative method to estimate CM effects when an initial treatment is quasi-randomly assigned, but a mediator mechanism is not, as is common in natural experiments.

econ.EM↗

arXiv2022

Market Interventions in a Large-Scale Virtual Economy

Massively multiplayer online role-playing games often contain sophisticated in-game economies. Many important real-world economic phenomena, such as inflation, economic growth, and business cycles, are also present in these virtual economies. One major difference between real-world and virtual economies is the ease and frequency by which a policymaker, in this case, a game developer, can introduce economic shocks. These economic shocks, typically implemented with game updates or signaled through community channels, provide fertile ground to study the effects of economic interventions on markets. In this work, we study the effect of in-game economic market interventions, namely, a transaction tax and an item sink, in Old School RuneScape. Using causal inference methods, we find that the tax did not meaningfully affect the trading volume of items at the tax boundaries and that the item sink contributed to the inflation of luxury good prices, without reducing trade volume. Furthermore, we find evidence that the illicit gold trading market was relatively unaffected by the implemented market interventions. Our findings yield useful insights not only into the effect of market interventions in virtual economies but also for real-world markets.

cs.HC↗