. Author manuscript; available in PMC: 2015 Mar 1.

Published in final edited form as: Int J Drug Policy. 2014 Jan 18;25(2):308–319. doi: 10.1016/j.drugpo.2014.01.003

Table 5.

Mediation Analysis of the Effects of Medical Marijuana Laws on Potency (THC%), 1990-2010

Variables	Total Effects (τ)	Direct Effects (τ′)	Indirect Effects (τ - τ′)
Panel A
Medical Marijuana Law	0.53 (0.55)	-0.09 (0.30)	0.61 (0.35)^*
Decriminalization Policy	2.62 (1.05)^**	0.93 (0.67)	1.70 (0.50)^***
Log Outdoor Plots Seized per 100,000 Population (Lagged 1 Year)	0.01(0.16)	-0.09 (0.12)	0.10 (0.10)
Log Indoor Grows Seized per 100,000 Population (Lagged 1 Year)	-0.27 (0.15)^*	-0.13 (0.15)	-0.14 (0.09)
Sinsemilla %		0.07 (0.01)^***
Mid-Grade %		0.00 (0.00)
Log Mean Kilograms Seized		-0.06 (0.03)^*
Constant	38.63 (52.14)	3.47 (41.74)
Adj. R²	33.9%	35.4%

Panel B
Legally Operating Dispensaries	0.99 (0.46)^**	-0.02 (0.36)	1.01 (0.32)^***
Home Cultivation	0.46 (0.51)	-0.26 (0.30)	0.72 (0.28)^***
Decriminalization Policy	2.79 (1.06)^**	0.94 (0.71)	1.86 (0.49)^***
Log Outdoor Plots Seized per 100,000 Population (Lagged 1 Year)	-0.02 (0.18)	-0.09 (0.12)	0.06 (0.10)
Log Indoor Grows Seized per 100,000 Population (Lagged 1 Year)	-0.19 (0.15)	-0.14 (0.16)	-0.06 (0.08)
Sinsemilla %		0.07 (0.01)^***
Mid-Grade %		0.00 (0.00)
Log Mean Kilograms Seized		-0.06 (0.03)^**
Constant	18.40 (57.30)	10.66 (45.61)
R²_adj	33.9%	35.4%

Note: Cluster robust standard errors are reported in parentheses. All models include state and year fixed effects and control variables. N = 39,157.

Significance levels:

10%,

^**

5%,

^***