Year	Percent change (Units)
1998	21.793
1999	-5.775
2000	-15.982
2001	20.460
2002	-32.995
2003	15.660
2004	0.428
2005	-21.634
2006	-38.219
2007	-21.088
2008	-19.265
2009	53.197
2010	-6.838
2011	-21.359
2012	4.914
2013	17.767
2014	8.989
2015	6.698
2016	-4.262
2017	-10.758
2018	14.754
2019	5.365