Year	Percent change (Units)
1980	18.361
1981	26.731
1982	-1.202
1983	4.812
1984	3.166
1985	0.921
1986	8.011
1987	17.687
1988	5.896
1989	7.860
1990	4.324
1991	5.626
1992	5.142
1993	1.747
1994	2.661
1995	1.672
1996	-0.082
1997	5.103
1998	4.386
1999	0.000
2000	4.116
2001	2.314
2002	2.262
2003	2.949
2004	0.806
2005	1.865
2006	1.918
2007	4.106
2008	5.834
2009	2.427
2010	3.291
2011	1.197
2012	0.798
2013	1.511
2014	1.063
2015	1.473
2016	2.142
2017	3.315
2018	1.899
2019	3.470
2020	6.584
2021	0.699
2022	11.227
2023	11.308
2024	7.118
2025	4.890
2026	3.915
2027	3.915
2028	3.915
2029	3.915