Year	Percent change (Units)
1980	16.849
1981	12.189
1982	8.511
1983	5.198
1984	4.448
1985	5.160
1986	3.626
1987	4.066
1988	4.612
1989	5.216
1990	6.999
1991	7.519
1992	4.232
1993	2.533
1994	1.994
1995	2.630
1996	2.425
1997	1.825
1998	1.557
1999	1.329
2000	0.796
2001	1.234
2002	1.259
2003	1.362
2004	1.344
2005	2.057
2006	2.329
2007	2.323
2008	3.602
2009	2.165
2010	3.298
2011	4.464
2012	2.828
2013	2.565
2014	1.461
2015	0.040
2016	0.660
2017	2.683
2018	2.478
2019	1.791
2020	0.851
2021	2.588
2022	9.067
2023	7.306
2024	2.453
2025	2.010
2026	2.000
2027	2.000
2028	2.000
2029	2.000