Year	Percent change (Units)
1980	10.912
1981	13.643
1982	11.341
1983	8.465
1984	6.218
1985	5.715
1986	7.176
1987	8.717
1988	6.676
1989	4.546
1990	4.131
1991	3.438
1992	2.328
1993	2.288
1994	1.376
1995	2.460
1996	1.263
1997	2.567
1998	2.252
1999	2.366
2000	3.086
2001	3.004
2002	1.287
2003	2.488
2004	0.454
2005	1.532
2006	2.329
2007	0.713
2008	3.754
2009	2.197
2010	2.419
2011	1.285
2012	0.697
2013	2.120
2014	2.042
2015	2.171
2016	3.550
2017	1.875
2018	2.765
2019	2.168
2020	1.287
2021	3.484
2022	5.764
2023	5.518
2024	3.300
2025	2.600
2026	2.000
2027	2.000
2028	2.000
2029	2.000