Year	Percent
1973-01-01	0.51315500000000000
1974-01-01	0.48431899999999994
1975-01-01	0.26314899999999997
1976-01-01	0.32453300000000000
1977-01-01	17.14880000000000000
1978-01-01	19.28050000000000000
1979-01-01	26.60280000000000000
1980-01-01	28.07860000000000000
1981-01-01	29.65560000000000000
1982-01-01	35.40020000000000000
1983-01-01	37.99820000000000000
1984-01-01	38.40170000000000000
1985-01-01	37.54800000000000000
1986-01-01	37.42670000000000000
1987-01-01	36.16870000000000000
1988-01-01	33.62440000000000000
1989-01-01	33.45740000000000000
1990-01-01	30.44950000000000000
1991-01-01	28.80180000000000000
1992-01-01	27.65960000000000000
1993-01-01	27.66430000000000000
1994-01-01	28.34730000000000000
1995-01-01	26.85820000000000000
1996-01-01	26.85480000000000000
1997-01-01	26.85480000000000000
1998-01-01	29.03010000000000000
1999-01-01	22.84610000000000000
2000-01-01	25.04470000000000000
2001-01-01	20.77500000000000000
2002-01-01	21.16220000000000000
2003-01-01	21.75260000000000000
2004-01-01	20.74590000000000000
2005-01-01	19.92470000000000000
2006-01-01	22.19660000000000000
2007-01-01	23.96460000000000000
2008-01-01	24.82710000000000000
2009-01-01	27.51550000000000000
2010-01-01	28.49510000000000000
2011-01-01	27.49320000000000000
2012-01-01	26.66730000000000000
2013-01-01	27.40960000000000000
2014-01-01	28.26730000000000000
2015-01-01	28.05890000000000000
2016-01-01	26.97360000000000000