Year	Percent
1966-01-01	0.0657476
1967-01-01	0.0869433
1968-01-01	0.0812080
1969-01-01	0.0643184
1970-01-01	0.0534312
1971-01-01	0.0867779
1972-01-01	0.1478858
1973-01-01	0.1757196
1974-01-01	0.1517037
1975-01-01	0.2959201
1976-01-01	0.3459617
1977-01-01	0.3562513
1978-01-01	0.4440345
1979-01-01	0.5186981
1980-01-01	0.6694623
1981-01-01	1.0870390
1982-01-01	1.6415590
1983-01-01	2.1982750
1984-01-01	3.0339700
1985-01-01	3.3734480
1986-01-01	3.5053240
1987-01-01	2.7922480
1988-01-01	3.1089270
1989-01-01	2.8458880
1990-01-01	3.2259960
1991-01-01	3.2340790
1992-01-01	2.0752720