Year	Percent
1972	0.6665
1973	19.01
1974	27.02
1975	14.42
1976	1.999
1977	0.8849
1978	3.704
1979	1.967
1980	4.717
1981	5.699
1982	9.815
1983	7.283
1984	8.265
1985	3.313
1986	7.153
1987	9.703
1988	11.8
1989	6.717
1990	10.28
1991	6.239
1992	15.32
1993	4.095
1994	5.551
1995	7.088
1996	6.897
1997	8.058
1998	7.579
1999	18.09
2000	21.56
2001	24.17
2002	21.84
2003	20.46
2004	30.11
2005	30.79
2006	36.13
2007	38.86