Table 1a. Interrupted Time-Series Regression Analysis of Adult Smoking Prevalence by Age Category, Pennsylvania, 1998-2010^a .

Variable	All Adults		18–39 y		≥40 y
	β	P Value	β	P Value	β	P Value
Base level (β0)	23.40	<.001	29.95	<.001	19.09	<.001
Base trend (β1)	0.07	.30	0.07	.49	0.08	.26
After 1st tax increase change in level (β21)	−0.52	.73	−2.35	.33	0.43	.79
After 1st tax increase change in trend (β31)	0.21	.54	1.08	.06	−0.22	.55
After 2nd tax increase change in level (β22)	−1.75	.14	−5.18	.010	−0.04	.98
After 2nd tax increase change in trend (β32)	−0.46	.18	−1.41	.01	0.02	.95

^a Adjusted for autocorrelation.