Table 2. Difference in Traffic Fatalities Between States Implementing RCLs and Synthetic Controls in the Postimplementation Period (2014-2017).

State by outcome	Mean post-RCL outcome gap	Pre-RCL MSPE	Post-RCL MSPE	Post-RCL:pre-RCL MSPE ratioa	Permutation ratio test resultb	Probability
Main analysis, fatalities per 1 billion VMT
Colorado	1.46	0.097	2.44	25.00	1/42	0.047
Washington State	0.08	0.16	0.31	1.88	28/42	0.674
Main analysis, age-adjusted rates (state population)
Colorado	0.98	0.07	1.47	22.24	3/42	0.093
Washington State	0.04	0.11	0.25	2.20	28/42	0.674
Using enactment date, fatalities per 1 billion VMT
Colorado	0.46	0.19	2.71	14.22	4/42	0.116
Washington State	0.25	0.08	0.20	2.99	23/42	0.558
Excluding neighbor states, fatalities per 1 billion VMT
Colorado	1.84	0.07	3.60	48.50	1/35	0.055
Washington State	0.07	0.17	0.31	1.86	30/41	0.738
Excluding non-MCL states, fatalities per 1 billion VMT
Colorado	2.16	0.19	4.98	25.89	0/15	0.063
Washington State	0.14	0.15	0.23	1.56	10/15	0.687

Abbreviations: MCL, medical cannabis law; MSPE, mean square prediction error; RCL, recreational cannabis law; VMT, vehicle miles traveled.

^aRatios were calculated prior to rounding.

^bIndicates the number of states (numerator) of included controls (denominator) with a post-RCL:pre-RCL MSPE ratio higher than or equal to that of Colorado or Washington State.