Poor housing conditions remain a major global public health challenge but direct causal evidence on their health effects is limited. We examine a rare rural housing intervention: the large-scale construction of subsidized high-quality cottages in Ireland 1883-1919. Using annual district-level data on deaths by cause, age and sex, we estimate the program's impact using difference-in-differences and triple-difference designs. Districts that built more cottages experienced mortality reductions of up to one death per thousand, driven by fewer respiratory deaths. The results are consistent with reduced indoor air pollution through improved ventilation. Cost-benefit analysis shows the scheme was highly cost-effective.

Evolutionary growth theory posits that natural selection set the stage for modern growth. I leverage micro-data from historical Germany to assess the viability of the selection mechanisms. I estimate fertility differentials and the inter-generational transmission of SES. High status couples, proxied by occupation, had 1-2 additional children, and SES was strongly heritable. To explore whether these parameters induce selection, I simulate an overlapping generation model of fertility choice and status transmission. The German parameters do not enable Clark's (2007) survival of the richest, whereas Galor and Moav's(2002) selection on quality can arise if the returns to investing in child quality are sufficiently large. Monte Carlo simulations extend the analysis beyond Germany. Survival of the richest requires exceptionally high coefficients of transmission (~0.87), and selection on quality emerges whenever returns to quality investments translate into higher fertility. Both depend on the strong heritability of the growth-complementary traits.

Soldiers in conscripted armies have low incentives to exert effort; the reward for doing so is small, and the potential cost (death) is incalculable. We investigate whether shared regional identity between soldiers and officers can alter the incentive problem. We test this hypothesis using data on all French WW1 fatalities. We use a data-driven approach to infer cultural regions from surnames. Soldiers and officers are considered aligned if they were born in the same region. We estimate the effect of losing alignment in a design-based difference-in-difference setup. Conditional on the regiment and battle, whether a dead officer was regionally connected is quasi-random. Within-regiment variation shows mortality declines among treated soldiers. The effect is concentrated among officers with distinctly regional names, that are non-migrants, supporting a behavioural mechanism. Our results suggest that shared identity with superiors incentivises agents to exert greater effort.