Year	Percent change (Units)
1980	18.774
1981	13.735
1982	-17.367
1983	-16.092
1984	19.799
1985	-14.036
1986	-2.452
1987	3.494
1988	21.909
1989	0.318
1990	-5.837
1991	2.143
1992	5.347
1993	7.018
1994	16.093
1995	16.791
1996	8.711
1997	5.385
1998	2.014
1999	-8.362
2000	5.338
2001	0.250
2002	5.342
2003	8.085
2004	15.508
2005	10.879
2006	18.261
2007	9.366
2008	2.809
2009	-17.660
2010	10.794
2011	11.838
2012	3.868
2013	4.039
2014	-0.687
2015	5.045
2016	-4.133
2017	1.533
2018	3.479
2019	0.553
2020	-17.577
2021	9.580
2022	14.893
2023	4.104
2024	4.005
2025	3.890
2026	3.832
2027	3.836
2028	3.836
2029	3.836