Year	Percent
1970	3.662
1971	40.98
1975	3.987
1977	4.016
1978	3.278
1979	3.298
1980	3.858
1981	29.46
1982	8.351
1983	13.65
1984	7.735
1985	7.03
1986	10.74
1987	9.909
1988	0.8101
1989	0.4879
1990	11.07
1991	6.18
1992	11.01
1993	7.529
1995	6.415
1996	16.84
1997	6.227
1998	11.37
1999	17.07
2000	14.96
2001	18.53
2002	24.75
2003	25.6
2004	43.73
2005	15.89
2006	16.06
2007	23.86