Consider the data on Walmart sales available in Walmart_2.xlsx Download Walmart_2.xlsx. Plot the quarterly sales data and verify that the series exhibits a seasonal element. Using the ESM contrast the additive seasonal, multiplicative seasonal, and logarithmic forms for forecasting sales, using the last 12 quarters as a hold-out sample.

Year	Walmart Stores	Super Stores	Sam's Club		Year	Quarter	Sales ($ billion)
1995	2176	154	453		2003	1	56.7
1996	2218	255	470		2003	2	62.6
1997	1960	344	436		2003	3	62.5
1998	1921	441	443		2003	4	74.5
1999	1860	564	451		2004	1	64.8
2000	1801	721	463		2004	2	69.7
2001	1736	888	475		2004	3	68.5
2002	1647	1066	500		2004	4	82.2
2003	1568	1258	525		2005	1	70.0
2004	1478	1471	538		2005	2	75.9
2005	1353	1713	551		2005	3	74.6
2006	1209	1980	567		2005	4	88.4
2007	1075	2256	579		2006	1	78.8
2008	971	2447	591		2006	2	84.5
2009	891	2612	602		2006	3	83.5
2010	708	2907	609		2006	4	98.1
2011	629	3029	611		2007	1	85.4
2012	561	3158	620		2007	2	92.0
2013	508	3288	632		2007	3	90.9
2014	470	3407	647		2007	4	106.3
2015	442	3465	655		2008	1	94.1
					2008	2	101.6
					2008	3	97.6
					2008	4	108.0
					2009	1	93.5
					2009	2	100.1
					2009	3	98.7
					2009	4	112.8
					2010	1	99.1
					2010	2	103
					2010	3	101.2
					2010	4	115.6
					2011	1	103.4
					2011	2	108.6
					2011	3	109.5
					2011	4	122.3
					2012	1	112.3
					2012	2	113.5
					2012	3	113.2
					2012	4	127.1
					2013	1	113.3
					2013	2	116.1
					2013	3	114.9
					2013	4	128.8
					2014	1	114.2
					2014	2	119.3
					2014	3	118.1
					2014	4	130.7
					2015	1	114
					2015	2	119.3
					2015	3	116.6
					2015	4	128.7