Year	Percent change (Units)
1980	33.610
1981	-3.143
1982	-9.255
1983	-6.800
1984	1.928
1985	2.367
1986	-30.361
1987	-8.427
1988	-2.027
1989	0.654
1990	16.925
1991	-9.654
1992	-3.093
1993	-8.719
1994	17.377
1995	27.851
1996	-7.913
1997	10.889
1998	3.069
1999	18.497
2000	33.157
2001	5.969
2002	-6.780
2003	20.844
2004	11.469
2005	32.814
2006	33.933
2007	-14.383
2008	21.686
2009	-42.828
2010	5.667
2011	38.071
2012	-3.820
2013	9.914
2014	-10.545
2015	-9.412
2016	-21.459
2017	7.016
2018	3.355
2019	-18.277
2020	-25.502
2021	44.067
2022	29.447
2023	-31.280
2024	-6.824
2025	5.904
2026	-0.276
2027	0.945
2028	2.012
2029	4.291