Rates of Change for CD's Sold
Year	Year (1990 set to 0)	Original Data	Linear Model	Exponential Model	Quadratic Model
1984	-6	5.8	62.14	7.13	14.87
1985	-5	22.6	62.14	10.76	24.324
1986	-4	53.0	62.14	16.22	33.778
1987	-3	102.1	62.14	24.46	43.232
1988	-2	149.7	62.14	36.88	52.686
1989	-1	207.2	62.14	55.61	62.14
1990	0	286.5	62.14	83.86	71.594
1991	1	333.3	62.14	126.45	81.048
1992	2	407.5	62.14	190.66	90.502
1993	3	495.4	62.14	287.50	99.956
1994	4	662.1	62.14	433.51	109.41
Linear Regression			Exponential regression
y'=62.14, r=.9748			y'=204.18*.4107e.4107x, r=.9383
Quadratic Regression
y'=4.727*2x+71.594, r=.9965
The rate of change data further indicates the conservative nature of the linear model with a moderate rate of chane in CD sales equal to 62.14 (million) per year.  The quadratic model, although it best fits the original data, is perhaps a bit too aggressive with an instantaneous rate of change equal to 109.41 million in 1994 (with x=4).