Year	Percent change (Units)
1980	10.667
1981	11.400
1982	4.898
1983	6.719
1984	3.208
1985	19.176
1986	32.780
1987	10.848
1988	10.295
1989	12.988
1990	37.977
1991	35.105
1992	10.245
1993	13.362
1994	12.510
1995	8.414
1996	11.054
1997	9.235
1998	6.615
1999	5.211
2000	5.979
2001	7.292
2002	8.126
2003	5.611
2004	7.573
2005	9.104
2006	6.564
2007	6.819
2008	11.360
2009	1.859
2010	3.858
2011	6.199
2012	3.800
2013	4.342
2014	3.420
2015	2.388
2016	4.447
2017	4.427
2018	3.749
2019	3.704
2020	3.211
2021	4.263
2022	6.882
2023	6.209
2024	4.025
2025	3.962
2026	3.990
2027	3.994
2028	4.033
2029	4.033