Year	Percent
1966-01-01	38.6999
1967-01-01	36.8686
1968-01-01	36.2696
1969-01-01	36.1858
1970-01-01	48.2931
1971-01-01	48.9296
1972-01-01	50.8120
1973-01-01	48.1347
1974-01-01	40.4199
1975-01-01	27.9274
1976-01-01	26.9144
1977-01-01	29.0423
1978-01-01	28.4996
1979-01-01	27.8051
1980-01-01	26.3605
1981-01-01	29.3248
1982-01-01	32.2399
1983-01-01	32.8608
1984-01-01	32.0486
1985-01-01	31.6914
1986-01-01	30.7137
1987-01-01	31.0684
1988-01-01	32.6235
1989-01-01	33.5431
1990-01-01	35.5490
1991-01-01	36.6242
1992-01-01	38.7357
1993-01-01	36.5603
1994-01-01	37.0452
1995-01-01	39.0924
1996-01-01	39.7159
1997-01-01	42.7010
1998-01-01	41.5813
1999-01-01	44.3443
2000-01-01	45.5058
2001-01-01	51.3697
2002-01-01	55.5658
2003-01-01	56.7289
2004-01-01	58.3940
2005-01-01	62.5579
2006-01-01	66.3632
2007-01-01	68.2476
2008-01-01	74.1047
2009-01-01	77.5214