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. Author manuscript; available in PMC: 2026 Jan 9.
Published in final edited form as: J Public Econ. 2025 Nov 18;252:105515. doi: 10.1016/j.jpubeco.2025.105515

Table 3.

Difference-in-Differences Estimates for Medicare Prescribing Outcomes.

Panel A: State and Time Fixed Effects
(1) (2) (3) (4)
Any Opioids Number of Prescriptions Days Supply MME
PMCL −0.006 (0.004) −0.031 (0.021) −0.577 (0.423) −0.815*** (0.284)
Counterfactual Mean 0.253 0.673 15.111 8.634
Implied Percent Change −2.402 −4.569 −3.815 −9.439
Panel B: + Demographic and Policy Controls
PMCL −0.006** (0.002) −0.035*** (0.010) −0.772*** (0.238) −0.925** (0.422)
Counterfactual Mean 0.252 0.677 15.306 8.744
Implied Percent Change −2.207 −5.187 −5.041 −10.575
Panel C: + OxyContin Misuse
PMCL −0.005*** (0.002) −0.035*** (0.008) −0.766*** (0.213) −0.928** (0.411)
Counterfactual Mean 0.252 0.676 15.300 8.748
Implied Percent Change −2.147 −5.111 −5.004 −10.612

Notes:

*

10%,

**

5%,

***

1% statistical significance. Standard errors (adjusted for state-level clustering) provided. All outcomes are per-beneficiary. We use two-stage difference-in-differences, weighted by the number of beneficiaries. Only states east of the Mississippi River are included in the analysis. In the first step, we regress the outcome on state fixed effects, time fixed effects, and covariates using only untreated observations. We use the estimates to impute the counterfactuals for the treated units. We regress the difference between the observed outcome and estimated counterfactual on whether the state had enacted a PMCL. “Demographic and Policy Controls” include share of the state population that is White, share of Medicare beneficiaries ages 65+, and policy variables. The policy variables are ACA Medicaid expansion, legal and operational medical marijuana dispensaries, recreational marijuana laws, must-access PDMPs, and opioid prescribing guidelines. Panel C includes controls for the interaction of the 2004–2009 non-medical OxyContin use rate with year indicators. The “Counterfactual Mean” is the mean of the outcome for all treated observations after subtracting off the estimated treatment effect. “Percent Change” is the implied percent change of the estimate given the counterfactual mean.