Year	Percent
1980	42.35946
1981	45.70409
1982	42.59743
1983	42.59316
1984	41.04449
1985	39.07829
1986	33.84727
1987	35.86035
1988	32.85615
1989	33.34014
1990	32.72344
1991	31.86051
1992	28.04777
1993	26.76879
1994	30.97432
1995	30.08255
1996	32.18957
1997	32.49172
1998	33.50851
1999	31.0507
2000	34.57535