Year	Percent change (Units)
1981	5.430
1982	5.230
1983	-0.180
1984	9.050
1985	20.470
1986	-11.820
1987	-4.660
1988	6.870
1989	11.050
1990	5.005
1991	44.996
1992	2.053
1993	4.714
1994	6.293
1995	14.835
1996	-8.999
1997	2.600
1998	2.300
1999	7.084
2000	-4.123
2001	-4.300
2002	14.002
2003	6.233
2004	7.852
2005	12.320
2006	18.519
2007	18.424
2008	39.245
2009	7.138
2010	14.564
2011	35.919
2012	15.000
2013	7.652
2014	7.114
2015	9.377
2016	6.152
2017	16.504
2018	10.581
2019	19.515
2020	18.169
2021	35.090
2022	33.806
2023	28.723
2024	21.533
2025	15.738
2026	13.860
2027	12.995
2028	11.869
2029	11.869