Year	Percent change (Units)
1980	7.910
1981	5.100
1982	9.000
1983	10.800
1984	15.200
1985	13.501
1986	8.900
1987	11.700
1988	11.200
1989	4.200
1990	3.888
1991	8.996
1992	14.277
1993	13.879
1994	13.029
1995	10.969
1996	9.921
1997	9.247
1998	7.856
1999	7.680
2000	8.472
2001	8.319
2002	9.115
2003	10.021
2004	10.114
2005	11.389
2006	12.710
2007	14.247
2008	9.592
2009	9.446
2010	10.611
2011	9.551
2012	7.848
2013	7.771
2014	7.391
2015	7.018
2016	6.851
2017	6.947
2018	6.751
2019	5.951
2020	2.242
2021	8.450
2022	2.989
2023	5.240
2024	4.642
2025	4.086
2026	3.770
2027	3.577
2028	3.380
2029	3.306