Year	Percent change (Units)
1980	1.467
1981	0.550
1982	-36.789
1983	22.710
1984	44.479
1985	24.300
1986	-6.773
1987	16.729
1988	-28.209
1989	-42.195
1990	-13.421
1991	38.200
1992	4.495
1993	7.000
1994	8.030
1995	6.493
1996	4.038
1997	10.190
1998	3.900
1999	-0.800
2000	1.100
2001	3.900
2002	3.400
2003	1.700
2004	7.500
2005	0.700
2006	1.549
2007	9.312
2008	9.067
2009	10.234
2010	7.974
2011	0.868
2012	2.564
2013	3.828
2014	2.485
2015	0.461
2016	1.556
2017	0.903
2018	-1.885
2019	-6.915
2020	-25.907
2021	-10.000