Year	Percent change (Units)
1980	18.121
1981	36.806
1982	90.271
1983	32.503
1984	12.013
1985	15.129
1986	11.788
1987	16.806
1988	20.845
1989	16.491
1990	19.069
1991	20.195
1992	21.788
1993	9.781
1994	13.534
1995	23.186
1996	17.512
1997	13.248
1998	11.660
1999	10.045
2000	10.961
2001	11.256
2002	9.167
2003	9.448
2004	12.315
2005	13.798
2006	11.471
2007	9.357
2008	13.425
2009	7.843
2010	5.663
2011	4.878
2012	4.496
2013	5.231
2014	4.519
2015	0.802
2016	-0.017
2017	1.626
2018	2.221
2019	2.096
2020	0.725
2021	1.727
2022	8.275
2023	0.525
2024	0.286
2025	2.917
2026	3.000
2027	3.000
2028	3.000
2029	3.000