Year	Percent change (Units)
1980	0.705
1981	-9.523
1982	20.759
1983	13.518
1984	-7.620
1985	3.649
1986	2.364
1987	2.800
1988	1.702
1989	4.331
1990	5.696
1991	2.163
1992	1.763
1993	3.833
1994	-3.398
1995	3.320
1996	2.906
1997	1.417
1998	6.500
1999	6.399
2000	5.525
2001	5.753
2002	-3.247
2003	6.874
2004	7.046
2005	-2.352
2006	-0.556
2007	3.043
2008	6.256
2009	6.666
2010	5.908
2011	-8.130
2012	5.242
2013	2.873
2014	-1.407
2015	4.058
2016	1.943
2017	4.823
2018	7.235
2019	6.222
2020	0.591
2021	5.256
2022	4.905
2023	5.555
2024	6.223
2025	5.788
2026	5.019
2027	5.020
2028	5.018
2029	5.018