From the paper: > Our second identification strategy, introduced by Troesken (2006) and Clay et al. (2014), exploits the fact that more lead particulate will l

From the paper: > Our second identification strategy, introduced by Troesken (2006) and Clay et al. (2014), exploits the fact that more lead particulate will leach into water with low pH levels. If lead exposure has a causal effect on homicide, more acidic water should be correlated with higher homicide rates only in cities that used lead water pipes. So there's more causal evidence than appears in the Mother Jones article. The two references for their "identification strategy" don't seem particularly well-cited though. [1][2] [1] http://www.mitpressjournals.org/doi/abs/10.1162/REST_a_00396 http://www.mitpressjournals.org/doi/abs/10.1162/REST_a_00396 [2] https://mitpress.mit.edu/books/great-lead-water-pipe-disaster https://mitpress.mit.edu/books/great-lead-water-pipe-disaste...