Year	Percent change (Units)
1980	13.704
1981	13.681
1982	12.034
1983	11.509
1984	10.550
1985	6.224
1986	3.711
1987	3.766
1988	3.811
1989	6.643
1990	10.834
1991	11.700
1992	9.450
1993	7.474
1994	10.671
1995	8.342
1996	0.851
1997	3.253
1998	3.816
1999	1.665
2000	-6.609
2001	-10.280
2002	-7.268
2003	-1.259
2004	-3.500
2005	9.812
2006	2.741
2007	7.332
2008	9.846
2009	0.328
2010	3.325
2011	26.646
2012	-3.674
2013	1.704
2014	7.138
2015	16.900
2016	23.983
2017	27.979
2018	-1.191
2019	0.214
2020	2.817
2021	3.702
2022	4.106
2023	2.564
2024	2.564
2025	2.564
2026	2.564
2027	2.564
2028	2.564
2029	2.564