Year	Percent change (Units)
1980	15.157
1981	12.017
1982	5.364
1983	5.333
1984	4.603
1985	5.611
1986	3.750
1987	3.715
1988	7.688
1989	5.503
1990	7.617
1991	7.203
1992	2.550
1993	2.409
1994	2.045
1995	2.952
1996	2.288
1997	1.710
1998	1.556
1999	1.124
2000	0.806
2001	1.059
2002	1.661
2003	1.270
2004	1.673
2005	1.918
2006	2.985
2007	2.083
2008	3.051
2009	2.894
2010	3.703
2011	4.197
2012	2.677
2013	2.034
2014	0.547
2015	0.202
2016	1.559
2017	2.973
2018	2.104
2019	1.302
2020	0.589
2021	5.386
2022	10.528
2023	3.993
2024	2.205
2025	2.000
2026	2.000
2027	2.000
2028	2.000
2029	2.000