Year	Percent change (Units)
1980	11.949
1981	10.285
1982	9.005
1983	12.083
1984	4.813
1985	7.833
1986	8.517
1987	9.485
1988	4.629
1989	6.049
1990	15.016
1991	13.385
1992	5.832
1993	9.509
1994	9.807
1995	8.820
1996	10.630
1997	9.044
1998	8.985
1999	3.685
2000	2.932
2001	5.611
2002	4.775
2003	3.851
2004	4.388
2005	4.085
2006	6.769
2007	6.446
2008	9.059
2009	12.575
2010	8.561
2011	7.773
2012	10.488
2013	7.663
2014	5.272
2015	5.259
2016	3.569
2017	4.594
2018	2.465
2019	6.668
2020	4.867
2021	6.344
2022	6.206
2023	5.071
2024	4.431
2025	4.119
2026	4.092
2027	4.000
2028	4.000
2029	4.000