Year	Percent
1966-01-01	1.2248500000000000
1967-01-01	1.3471000000000000
1968-01-01	1.4253799999999999
1969-01-01	1.3866100000000001
1970-01-01	1.4243200000000000
1971-01-01	1.4780000000000002
1972-01-01	1.5196100000000001
1973-01-01	1.4273000000000000
1974-01-01	1.4805000000000000
1975-01-01	1.6569099999999999
1976-01-01	1.8026099999999998
1977-01-01	2.0591800000000000
1978-01-01	2.3301900000000000
1979-01-01	2.6602799999999998
1980-01-01	2.8232600000000000
1981-01-01	3.1128299999999998
1982-01-01	3.4471100000000000
1983-01-01	3.7095200000000000
1984-01-01	4.0676100000000000
1985-01-01	4.3125300000000010
1986-01-01	4.7094100000000000
1987-01-01	5.0454200000000000
1988-01-01	4.8988400000000000