Year	Percent change (Units)
1980	31.238
1981	11.170
1982	20.687
1983	23.418
1984	23.599
1985	26.837
1986	17.349
1987	21.133
1988	12.300
1989	21.199
1990	27.235
1991	18.775
1992	12.932
1993	12.472
1994	9.166
1995	8.337
1996	6.695
1997	6.041
1998	4.663
1999	2.318
2000	4.554
2001	2.666
2002	2.866
2003	1.100
2004	2.444
2005	3.671
2006	2.607
2007	7.861
2008	7.089
2009	-1.507
2010	2.942
2011	4.389
2012	1.457
2013	3.056
2014	4.698
2015	4.427
2016	2.729
2017	2.260
2018	2.115
2019	2.950
2020	2.928
2021	7.137
2022	12.772
2023	3.929
2024	3.000
2025	3.000
2026	3.000
2027	3.000
2028	3.000
2029	3.000