Year	Years
1980	8.882
1981	9.002
1982	7.544
1983	7.912
1984	9.208
1985	9.372
1986	9.166
1987	8.874
1988	8.23
1989	8.036
1990	7.776
1991	7.338
1992	8.301
1993	7.313
1994	5.463
1995	4.876
1996	4.997
1997	4.748
1998	4.832
1999	3.981
2000	3.856
2001	3.301
2002	3.461
2003	4.261
2004	3.808