Regression Equation: Yt = β0 + β1Timet + β2Interventiont + β3Interventiont × Timet + β4Treatment + β5Treatment × Timet + β6Treatment × Intervention + β7Treatment × Interventiont × Timet + β8Quarter2 + β9Quarter3 +β10Quarter4 + Et
Coefficient	Description21
Control (nonexpansion states)
Baseline intercept (B0)	The intercept, or starting level of the outcome variable
Pre-expansion trend (B1)	The slope, or trajectory of the outcome variable until the introduction of the intervention
Expansion (B2)	The change in the level of the outcome that occurs in the period immediately following the introduction of the intervention
Expansion-trend (B3)	The difference between pre- and postintervention slopes of the outcome
Treatment (expansion states)
Baseline intercept (B4)	The difference in the level (intercept) of the outcome variable between treatment and controls prior to the intervention
Trend (B5)	The difference in the slope (trend) of the outcome variable between treatment and controls prior to the intervention
Expansion (B6)	The difference between treatment and control groups in the level of the outcome variable immediately following introduction of the intervention
Expansion-trend (B7)	The difference between treatment and control groups in the slope (trend) of the outcome variable after initiation of the intervention compared to pre-intervention (akin to a difference-in-differences of slopes)
Seasonality (reference category: quarter 1, January-March)
Quarter 2 (B8)	April-June
Quarter 3 (B9)	July-September
Quarter 4 (B10)	October-December