Year	Percent
1961-01-01	14.133520
1962-01-01	14.443430
1963-01-01	14.479510
1964-01-01	14.083020
1965-01-01	13.887320
1966-01-01	14.794510
1967-01-01	17.918530
1968-01-01	20.429810
1969-01-01	20.250370
1970-01-01	19.883890
1971-01-01	18.794090
1972-01-01	18.067470
1973-01-01	16.597990
1974-01-01	16.882400
1975-01-01	19.051450
1976-01-01	19.702260
1977-01-01	19.798550
1978-01-01	18.970310
1979-01-01	18.976830
1980-01-01	18.927110
1981-01-01	17.746940
1982-01-01	18.871470
1983-01-01	19.925630
1984-01-01	23.516460
1985-01-01	27.585000
1986-01-01	29.737870
1987-01-01	31.518710
1988-01-01	27.986460
1989-01-01	28.069590
1990-01-01	28.307760
1991-01-01	29.150950
1992-01-01	31.469140
1993-01-01	29.958740
1994-01-01	25.381570
1995-01-01	12.952590
1996-01-01	3.344821
1997-01-01	2.872643