# **A Supplementary Methods**

Each subsection details the construction of an outcome variable or set of outcome variables, the regression(s) on that outcome variable presented in the main text, and robustness checks for that outcome variable.

## **A.1 Elephant Poaching (Figure S1 and Table S6)**

The Monitoring the Illegal Killing of Elephants (MIKE) program records elephant deaths each year at sites across Africa and Asia. As of January 2023 when we downloaded the data, there were 96 sites, with data spanning from 2000 to 2021 [57]. Among the 66 African MIKE sites, 8 are currently managed by AP (treatment group), and 35 were among those identified by AP as “anchor areas” meeting their criteria for future management (control group). Our regression analysis includes 578 site-year observations from these 43 distinct sites (Figure S1). Table S6 displays Average Treatment effects on the Treated (ATTs) by “cohort”, or the calendar year in which protected areas are transferred to AP management.

MIKE data contain the total number of elephant carcasses discovered at a site in a year, as well the number of those carcasses that were killed illegally (poached). Dividing the number of poached carcasses by the total number of carcasses yields the Proportion of Illegally Killed Elephants (PIKE). This normalization controls for fluctuating survey efforts and elephant population sizes across sites and years under the following assumption: conditional on the number of poached and non-poached carcasses available for discovery, the probability of finding a poached carcass equals the probability of finding a non-poached one [102, 103]. Studies of MIKE sites corroborate that PIKE accurately reflects mortality patterns in the sense that PIKE is not confounded by changes in survey effort or in the underlying elephant population level [104, 105].

Even if the conditional probabilities of finding poached and non-poached carcasses differ, bias in our estimated impact of AP management on PIKE would only arise if AP management changes the probability of discovering a poached carcass relative to a non-poached one. AP management could theoretically increase or decrease the relative probability of finding a poached carcass. When a protected area has few rangers, all patrol effort may occur in “hotspot” locations where finding poached carcasses is likeliest. If AP increases the number of rangers on staff compared to governmentmanaged protected areas, those additional rangers could patrol locations where finding poached carcasses is less likely, and finding non-poached carcasses more likely. This change in where rangers patrol would mechanically reduce PIKE, even if the protected area’s true rate of poaching hasn’t changed. On the other hand, AP could increase the relative probability of finding poached carcasses if it is better able to target ranger patrols to hotspot locations. This change in where rangers patrol would mechanically increase PIKE. While we cannot test for changes in where rangers patrol due to these data being non-public, we can test whether AP management affects the probability of reporting any MIKE data in a given year. We find no evidence that AP management significantly influences the probability of reporting carcass data to MIKE: the ATT is -0.055 with a standard error of 0.142.

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