Year	Percent change (Units)
1980	35.138
1981	19.687
1982	9.941
1983	27.257
1984	19.860
1985	30.703
1986	19.477
1987	19.881
1988	14.684
1989	17.028
1990	26.036
1991	21.815
1992	15.454
1993	12.743
1994	11.460
1995	8.229
1996	7.356
1997	6.127
1998	5.106
1999	3.333
2000	3.838
2001	3.565
2002	2.486
2003	2.811
2004	1.053
2005	3.053
2006	3.402
2007	4.413
2008	8.723
2009	1.498
2010	1.408
2011	3.335
2012	2.999
2013	1.789
2014	4.714
2015	4.349
2016	3.789
2017	2.183
2018	2.317
2019	2.249
2020	3.043
2021	4.524
2022	11.645
2023	7.583
2024	3.180
2025	3.000
2026	3.000
2027	3.000
2028	3.000
2029	3.000