Year	Percent
1973-01-01	51.2507
1974-01-01	44.1555
1975-01-01	33.2379
1976-01-01	33.2771
1977-01-01	36.0793
1978-01-01	36.8328
1979-01-01	36.6128
1980-01-01	33.4974
1981-01-01	36.6275
1982-01-01	40.2679
1983-01-01	41.0066
1984-01-01	40.3201
1985-01-01	40.7082
1986-01-01	40.1055
1987-01-01	41.0412
1988-01-01	43.0175
1989-01-01	42.9524
1990-01-01	45.1445
1991-01-01	47.2997
1992-01-01	51.4339
1993-01-01	50.4815
1994-01-01	50.9317
1995-01-01	53.5274
1996-01-01	56.5040
1997-01-01	62.0584
1998-01-01	58.1465
1999-01-01	59.2116
2000-01-01	60.9288
2001-01-01	69.3479
2002-01-01	75.4346
2003-01-01	79.1559
2004-01-01	81.8171
2005-01-01	84.7608
2006-01-01	85.5655
2007-01-01	86.1190
2008-01-01	93.5706
2009-01-01	97.4630