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Volume
8: No. 1, January 2011
LETTER
Regression Model Fitting With Quadratic Term Leads to Different Conclusion in Economic Analysis of Washington State Smoking Ban
| Quarter/Year |
Sales in Millions, $ |
Linear |
Quadratic |
| 1/02 |
96.5 |
89.2 |
101.0 |
| 2/02 |
98.7 |
90.0 |
98.8 |
| 3/02 |
99.7 |
90.8 |
96.7 |
| 4/02 |
95.1 |
91.6 |
95.0 |
| 1/03 |
91.1 |
92.4 |
93.6 |
| 2/03 |
91.9 |
93.3 |
92.5 |
| 3/03 |
93.3 |
94.1 |
91.6 |
| 4/03 |
92.6 |
94.9 |
91.0 |
| 1/04 |
90.0 |
95.7 |
90.7 |
| 2/04 |
92.2 |
96.5 |
90.7 |
| 3/04 |
97.1 |
97.3 |
90.9 |
| 4/04 |
93.4 |
98.2 |
91.5 |
| 1/05 |
91.5 |
99.0 |
92.3 |
| 2/05 |
96.6 |
99.8 |
93.4 |
| 3/05 |
99.3 |
100.6 |
94.8 |
| 4/05 |
96.9 |
101.4 |
96.4 |
| 1/06 |
91.8 |
102.2 |
98.4 |
| 2/06 |
96.3 |
103.1 |
100.6 |
| 3/06 |
99.4 |
103.9 |
103.1 |
| 4/06 |
97.6 |
104.7 |
105.9 |
| 1/07 |
100.3 |
105.5 |
108.9 |
| 2/07 |
114.1 |
106.3 |
112.3 |
| 3/07 |
126.0 |
107.1 |
115.9 |
| 4/07 |
124.2 |
108.0 |
119.8 |
Figure. Comparison of regression fit to taxable retail
sales in bars and taverns in Washington State after the implementation of a
smoke-free law, from the first quarter of 2002 (1/02) through the fourth quarter
of 2007 (4/07). Values are adjusted for inflation to the
Consumer Price Index (www.bls.gov/cpi/). The figure displays 2 regression equations for the quadratic fitting (y =
0.1405x2
− 2.4969x + 103.58, R2 = 0.7811) and the linear fitting (y = 0.8166x + 88.359, R2
= 0.367) .
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