Year	Percent
1967-01-01	3.01694847502148
1968-01-01	4.09389143106834
1969-01-01	2.62934083658333
1970-01-01	4.65229749303156
1971-01-01	4.78411438154618
1972-01-01	6.67117766528365
1973-01-01	13.61831734583800
1974-01-01	23.55268738502770
1975-01-01	16.77357032458170
1976-01-01	9.79365327534655
1977-01-01	10.68895742077510
1978-01-01	10.30612922229660
1979-01-01	14.72217036899920
1980-01-01	17.91992414062670
1981-01-01	14.33188660093940
1982-01-01	7.81274141216488
1983-01-01	10.24366335265450
1984-01-01	11.50716950573080
1985-01-01	12.95885574361430
1986-01-01	9.76521367907860
1987-01-01	11.53753613378940
1988-01-01	8.01262890572416
1989-01-01	11.40963200657620
1990-01-01	21.50798817326790
1991-01-01	21.61574359664460
1992-01-01	10.63019968930370
1993-01-01	10.26504657917810
1994-01-01	9.70025033516308
1995-01-01	10.19320676307460
1996-01-01	7.35911744357080
1997-01-01	6.94956608534118
1998-01-01	5.11024301619077
1999-01-01	3.48672890200982
2000-01-01	4.60822998872596
2001-01-01	4.35934065217273
2002-01-01	3.75017465778467
2003-01-01	3.81110624396873
2004-01-01	4.32326492967493
2005-01-01	4.69094870903770
2006-01-01	4.25195321977968
2007-01-01	4.57808572377153
2008-01-01	8.10810810810780
2009-01-01	2.50049995050118
2010-01-01	3.43650905943355
2011-01-01	4.97773563706971
2012-01-01	3.78250023985418
2013-01-01	2.52864788538364
2014-01-01	3.22604678885414
2015-01-01	2.12849239904152
2016-01-01	1.72826463324536
2017-01-01	2.61799921819100