Year	Percent
1961-01-01	2.5982300000000000
1962-01-01	2.8681600000000000
1963-01-01	3.1275900000000000
1964-01-01	3.1611800000000000
1965-01-01	3.3289900000000000
1966-01-01	3.6950000000000000
1967-01-01	4.0613600000000000
1968-01-01	4.4601600000000000
1969-01-01	4.2570800000000000
1970-01-01	4.2379000000000000
1971-01-01	4.2943100000000000
1972-01-01	4.4381699999999995
1973-01-01	4.4796400000000000
1974-01-01	4.5812700000000000
1975-01-01	4.9262300000000000
1976-01-01	5.0476700000000000
1977-01-01	5.1934900000000000
1978-01-01	5.4062300000000000
1979-01-01	5.7241200000000000
1980-01-01	6.1437599999999990
1981-01-01	6.7156100000000010
1982-01-01	7.3616800000000010
1983-01-01	7.7369900000000000
1984-01-01	7.9399600000000010
1985-01-01	8.3396900000000000
1986-01-01	8.6824200000000000
1987-01-01	8.9693600000000000
1988-01-01	9.2021000000000000
1989-01-01	9.2195700000000000
1990-01-01	9.1831500000000000
1991-01-01	9.3133200000000000
1992-01-01	9.6080600000000000
1993-01-01	9.7336900000000000
1994-01-01	9.3933400000000000
1995-01-01	8.9748000000000000
1996-01-01	8.8649100000000000
1997-01-01	8.5251000000000000
1998-01-01	8.1970200000000000