I'm having trouble computing the mean absolute percentage error (MAPE) for an exponential curve.

The data presented in column 1 is the year, and column 2 is Revenue.

Suppose my data starts in year 1 and extends to year 50. I have corresponding yearly sales data,

Utilizing the Exponential function y=ae^(bx) what is my yearly forecast? And the Mean Absolute Percentage Error?

Example: apparently my Exponential Forecast and Absolute Error are incorrect.

Year Count	Average of Seasonally Adjusted Sales	YoY Growth (Actual)	Exponential Forecast	Absolute % Error
1	$150,781.17
2	$161,696.25	7.2%	$172,399	6.6%
3	$175,688.83	8.7%	$179,974	2.4%
4	$185,437.25	5.5%	$187,882	1.3%
5	$196,728.17	6.1%	$196,137	0.3%
6	$206,334.08	4.9%	$204,755	0.8%
7	$215,657.67	4.5%	$213,751	0.9%
8	$233,872.00	8.4%	$223,143	4.6%
9	$248,748.25	6.4%	$232,948	6.4%
10	$255,663.75	2.8%	$243,183	4.9%
11	$261,272.42	2.2%	$253,868	2.8%
12	$272,232.50	4.2%	$265,022	2.6%
13	$288,987.50	6.2%	$276,667	4.3%
14	$307,826.08	6.5%	$288,823	6.2%
15	$323,823.08	5.2%	$301,513	6.9%
16	$334,008.00	3.1%	$314,761	5.8%
17	$328,780.33	-1.6%	$328,591	0.1%
18	$303,288.92	-7.8%	$343,029	13.1%
19	$323,964.17	6.8%	$358,100	10.5%
20	$349,717.75	7.9%	$373,835	6.9%