Year	Percent change (Units)
1981	2.500
1982	2.000
1983	2.000
1984	2.700
1985	9.300
1986	6.500
1987	7.300
1988	18.800
1989	18.000
1990	3.315
1991	3.562
1992	6.358
1993	14.624
1994	24.260
1995	16.767
1996	8.303
1997	2.778
1998	-0.781
1999	-1.401
2000	0.348
2001	0.724
2002	-0.769
2003	1.163
2004	3.895
2005	1.809
2006	1.468
2007	4.772
2008	5.844
2009	-0.692
2010	3.329
2011	5.416
2012	2.620
2013	2.627
2014	1.994
2015	1.443
2016	1.996
2017	1.579
2018	2.093
2019	2.905
2020	2.492
2021	0.918
2022	1.975
2023	0.228
2024	0.970
2025	1.993
2026	1.951
2027	1.951
2028	1.951
2029	1.951