Year	Percent change (Units)
1981	15.500
1982	8.000
1983	-26.800
1984	65.300
1985	-31.500
1986	-6.500
1987	28.800
1988	20.900
1989	-16.300
1990	40.900
1991	5.903
1992	-70.657
1993	164.628
1994	134.584
1995	-31.699
1996	-12.906
1997	115.636
1998	-19.589
1999	64.977
2000	21.433
2001	10.577
2002	-11.488
2003	-4.657
2004	8.780
2005	18.526
2006	-13.292
2007	13.435
2008	0.245
2009	20.129
2010	-10.080
2011	44.895
2012	-12.371
2013	4.253
2014	6.797
2015	7.603
2016	-2.371
2017	7.807
2018	34.116
2019	9.901
2020	-5.487
2021	21.442
2022	-26.618
2023	0.514
2024	20.740
2025	3.483
2026	2.186
2027	2.147
2028	2.629
2029	2.209