Year	Percent
1961-01-01	28.0433
1962-01-01	28.8236
1963-01-01	29.4103
1964-01-01	29.7575
1965-01-01	30.7391
1966-01-01	31.9726
1967-01-01	33.3802
1968-01-01	34.5967
1969-01-01	34.5800
1970-01-01	34.4856
1971-01-01	34.6922
1972-01-01	34.8330
1973-01-01	34.1041
1974-01-01	33.9119
1975-01-01	34.1143
1976-01-01	34.1482
1977-01-01	31.8647
1978-01-01	28.3583
1979-01-01	28.8848
1980-01-01	29.2894
1981-01-01	29.3588
1982-01-01	29.6499
1983-01-01	30.4729
1984-01-01	31.4908