Year	Percent
1969-01-01	2.03876600198418
1970-01-01	1.41258924956405
1971-01-01	1.23853108826759
1972-01-01	1.16441848279074
1973-01-01	1.08489617598987
1974-01-01	1.34543615207231
1975-01-01	1.75242410549895
1976-01-01	1.80901774661527
1977-01-01	1.63816254582151
1978-01-01	2.06265552371872
1979-01-01	2.10419540254475
1980-01-01	1.85427695318009
1981-01-01	2.51560925624183
1982-01-01	3.46495914690694
1983-01-01	4.10756086309384
1984-01-01	3.80004518678982
1985-01-01	3.59938423546055
1986-01-01	3.13463150943443
1987-01-01	3.79492352401234
1988-01-01	3.56373374586505
1989-01-01	3.13262777407493
1990-01-01	3.24046173228391
1991-01-01	3.47567583625191
1992-01-01	3.59314564383555
1993-01-01	4.21746608135019
1994-01-01	3.57794177705799
1995-01-01	3.69978496409736
1996-01-01	4.13983054615580
1997-01-01	4.24240647147961
1998-01-01	4.23576622704515
1999-01-01	3.72796739498001
2000-01-01	3.53302473775476
2001-01-01	3.59086010291845
2002-01-01	3.95197778859409
2003-01-01	4.28648720316126
2004-01-01	5.49024955846798
2005-01-01	5.62841708394799
2006-01-01	5.24671858750928
2007-01-01	4.85895167986160
2008-01-01	4.12910382097195
2009-01-01	5.29898788025976
2010-01-01	4.82168022671987
2011-01-01	4.56662190017683
2012-01-01	4.86326672371018
2013-01-01	5.33603098735848
2014-01-01	5.62121906196362
2015-01-01	5.72346762763626
2016-01-01	6.01407095256530
2017-01-01	5.50052803038633