Year	Percent change (Units)
1980	0.887
1981	6.936
1982	-12.630
1983	26.392
1984	1.875
1985	-8.197
1986	4.205
1987	28.027
1988	33.706
1989	21.793
1990	22.037
1991	9.452
1992	5.222
1993	10.152
1994	15.724
1995	19.338
1996	1.117
1997	-7.787
1998	-24.071
1999	12.480
2000	6.920
2001	-3.418
2002	3.797
2003	13.457
2004	20.557
2005	18.606
2006	1.197
2007	3.435
2008	12.431
2009	-20.397
2010	27.287
2011	13.465
2012	6.653
2013	2.019
2014	-6.761
2015	-0.683
2016	-2.476
2017	7.368
2018	7.650
2019	-5.821
2020	-10.467
2021	17.914
2022	1.209
2023	-3.638
2024	3.600
2025	3.800
2026	3.750
2027	3.500
2028	3.500
2029	3.500