Table 1.

Predictors included as fixed effects in the final modeling approach.

Predictor	Description	Source*
Healthcare access
Buprenorphine waivered physicians	Crude number of active buprenorphine waivered physicians each year	SAMHSA
Urgent Care Presence	Presence of an Urgent Care facility within county	HSIP Gold
Drug markets
Opioid Prescription Rate	Opioid prescribing rate per 100 people each year	CDC (IQVIA Xponent)
Log Fentanyl Seizure Data	State-level count of fentanyl tested in local-, state-, and federal-level forensic labs each year	NFLIS
Log Jail Population Size	The log of the jail population size	VERA
Socio-economic indicators
High School Graduation Rate	Proportion of people living in the county estimated to have graduated from high school or received an equivalent certification.	ACS
Poverty Rate	Proportion of households in the county estimated to be living at or below the poverty line.	ACS
Unemployment Rate	Proportion of people able to work in the county estimated to be unemployed.	ACS
Employee capacity Difference	Difference in the employment capacity (measured as number of staff employed) of all companies across industries between current and past year in the county.	CBP
Payroll Difference	Difference in payroll (measured in US dollars) of all companies across industries between current and past year in the county.	CBP
Log Median Household Income	The logarithm of the estimated median household income in the county.	ACS
Proportion of Homeowner Households That Spend At Least 35% of Income on Mortgage	The proportion of homeowner households in the county where it estimated that the household spends at least 35% of their income on their mortgage.	ACS
Proportion of Renter Household That Spend At Least 35% of Income on Rent	The proportion of renter households in the county where it estimated that the household spends at least 35% of their income on their rent.	ACS
Geographic Spread of Epidemic
Log Overdose Gravity	Continuous variable generated to operationalize overdose death rates in neighboring counties. To derive the gravity variable for a given county x in year t, we first identified the set of all counties Y within 200 miles of county x. Distances were measured from central, internal points in each county and were extracted from a dataset created by the National Bureau of Economic Research. Second, for each county y in Y, we divided the overdose death rate for county y in the year t by the distance between counties x and y, squared. Third, we summed the values calculated in the previous step for each county y in Y. Finally, we took the natural logarithm of this summed value to get the final value.	NBER
Urbanicity	Six category variable based on US Office of Management and Budget 2013 determination of metropolitan statistical areas, coded on a spectrum from most urban (1) to most rural (6).	NCHS

^*Detailed source information for each variable is provided in the Supplement Page 3.

ACS: Census American Community Survey; NFLIS: National Forensic Laboratory Information System; CBP: County Business Patterns; NCHS: National Center for Health Statistics; SAMHSA: Substance Use and Mental Health Services Administration; HSIP: Homeland Security Infrastructure Program; VERA: VERA Institute of Justice; NBER: National Bureau of Economic Research