Year	Percent
1991-01-01	17.9689998626709
1992-01-01	18.6410007476807
1993-01-01	22.7600002288818
1994-01-01	20.8040008544922
1995-01-01	18.5900001525879
1996-01-01	19.2509994506836
1997-01-01	16.8449993133545
1998-01-01	15.2510004043579
1999-01-01	12.3000001907349
2000-01-01	12.3109998703003
2001-01-01	10.6289997100830
2002-01-01	11.3479995727539
2003-01-01	12.7980003356934
2004-01-01	14.3520002365112
2005-01-01	19.3610000610352
2006-01-01	19.1590003967285
2007-01-01	18.0890007019043
2008-01-01	19.5809993743896
2009-01-01	26.5069999694824
2010-01-01	26.4680004119873
2011-01-01	25.9950008392334
2012-01-01	28.1739997863770
2013-01-01	26.5090007781982
2014-01-01	20.3309993743896
2015-01-01	17.2019996643066
2016-01-01	12.8520002365112
2017-01-01	10.6890001296997