Year	Percent change (Units)
1980	14.031
1981	-10.227
1983	10.127
1984	3.448
1985	11.111
1986	1.000
1988	-4.950
1989	-6.250
1990	5.600
1991	13.200
1992	15.700
1993	17.100
1994	12.200
1995	2.662
1996	0.338
1997	12.360
1998	8.500
1999	0.184
2000	12.971
2001	4.971
2002	-11.833
2003	9.876
2004	20.171
2005	-4.141
2006	7.620
2007	-1.846
2008	8.837
2009	-27.574
2010	16.520
2011	35.261
2012	-18.909
2013	1.635
2014	12.244
2015	17.994
2016	8.274
2017	2.594
2018	-0.902
2019	-7.757
2020	-20.423
2021	-5.118
2022	-22.385