Year	Percent change (Units)
1998	-39.106
1999	-39.409
2000	22.511
2001	-3.823
2002	7.163
2003	-28.238
2004	9.100
2005	3.300
2006	14.610
2007	-16.795
2008	-34.228
2009	2.769
2010	2.233
2011	501.700
2012	0.050
2013	-58.545
2014	163.921
2015	-35.770
2016	-33.960
2017	68.592
2018	24.424
2019	29.801