Year	Percent change (Units)
1991	9.572
1992	8.232
1993	17.349
1994	14.051
1995	9.341
1996	4.923
1997	1.605
1998	-2.241
1999	-3.700
2000	-3.900
2001	8.453
2002	-0.515
2003	4.823
2004	9.997
2005	4.921
2006	6.712
2007	4.774
2008	15.393
2009	1.722
2010	6.321