Year	Percent change (Units)
1980	22.535
1981	13.793
1982	5.374
1983	12.807
1984	20.938
1985	24.845
1986	31.697
1987	21.658
1988	22.594
1989	25.592
1990	38.162
1991	24.275
1992	15.105
1993	18.277
1994	20.596
1995	13.387
1996	9.798
1997	6.950
1998	11.554
1999	6.751
2000	8.984
2001	7.314
2002	10.472
2003	14.239
2004	4.310
2005	6.823
2006	9.565
2007	8.144
2008	10.186
2009	2.606
2010	4.636
2011	8.244
2012	3.692
2013	2.662
2014	5.028
2015	3.132
2016	4.082
2017	3.614
2018	3.972
2019	2.757
2020	1.768
2021	4.788
2022	9.766
2023	4.632
2024	3.837
2025	4.000
2026	4.000
2027	4.000
2028	4.000
2029	4.000