Year	Percent change (Units)
1981	-11.153
1982	-11.868
1983	-9.480
1984	-9.630
1985	-3.491
1986	1.647
1987	16.281
1988	6.559
1989	95.243
1990	16.647
1991	-12.461
1992	-11.087
1993	10.631
1994	-0.793
1995	3.441
1996	3.401
1997	2.163
1998	-10.286
1999	11.277
2000	9.966
2001	19.729
2002	18.739
2003	-20.539
2004	8.117
2005	10.493
2006	3.482
2007	3.596
2008	10.511
2009	-16.819
2010	18.283