Year	Percent
1971-01-01	21.571470
1972-01-01	17.199010
1973-01-01	17.117490
1974-01-01	18.447350
1975-01-01	17.750050
1976-01-01	17.875470
1977-01-01	18.540640
1978-01-01	19.572920
1979-01-01	20.854130
1980-01-01	21.618370
1981-01-01	21.143910
1982-01-01	22.149140
1983-01-01	23.581720
1984-01-01	25.203570
1985-01-01	26.164410
1986-01-01	24.676740
1987-01-01	24.070080
1988-01-01	23.677040
1989-01-01	23.414020
1990-01-01	23.411410
1991-01-01	25.442840
1992-01-01	26.932240
1993-01-01	27.057980
1994-01-01	26.956940
1995-01-01	14.200200
1996-01-01	1.456599
1997-01-01	1.466575
1998-01-01	1.563281