Year	Percent
1979-01-01	3.13736035095008
1980-01-01	3.11023085953934
1981-01-01	3.13165467032792
1982-01-01	4.21942840863446
1983-01-01	6.82604476315231
1984-01-01	6.11602226235356
1985-01-01	5.74431187857074
1986-01-01	5.49440830544250
1987-01-01	5.72485724603767
1988-01-01	4.95040177018404
1989-01-01	4.36231005852427
1990-01-01	4.99535648727565
1991-01-01	7.67204374186238
1992-01-01	8.92926122941146
1993-01-01	9.49005304720449
1994-01-01	8.15568638152793
1995-01-01	7.09989385800120
1996-01-01	6.89129539654473
1997-01-01	6.69762305989903
1998-01-01	6.32250026859940
1999-01-01	5.58767449664816
2000-01-01	5.07564747775105
2001-01-01	5.33032726728068
2002-01-01	4.97350160170225
2003-01-01	4.44369594489218
2004-01-01	3.87167753836030
2005-01-01	3.58015803639450
2006-01-01	3.39618789484414
2007-01-01	2.87201009521293
2008-01-01	2.85869033362254
2009-01-01	4.25614692715083
2010-01-01	3.66225857921329
2011-01-01	3.48504934234476
2012-01-01	3.69415348659251
2013-01-01	4.28921806162316
2014-01-01	4.44476584532213
2015-01-01	4.46545871277943
2016-01-01	4.10074426259664
2017-01-01	3.99276728340324