Year	Percent change (Units)
1980	-1.900
1981	-2.800
1982	4.200
1983	3.500
1984	-4.200
1985	12.100
1986	-7.600
1987	17.600
1988	14.100
1989	18.800
1990	8.877
1991	-5.750
1992	-0.446
1993	13.003
1994	3.821
1995	-1.029
1996	-0.986
1997	-0.624
1998	-1.237
1999	4.270
2000	4.423
2001	17.567
2002	15.286
2003	-22.391
2004	16.425
2005	6.963
2006	0.694
2007	7.116
2008	5.126
2009	-4.604
2010	11.328