Year	Percent
1978-01-01	2.38204717741866
1979-01-01	2.16157236256132
1980-01-01	2.04140942289786
1981-01-01	2.27072255547294
1982-01-01	2.40324110568896
1983-01-01	2.68295819055203
1984-01-01	2.69414455090806
1985-01-01	2.61073803282377
1986-01-01	2.75444962207121
1987-01-01	2.88291047557466
1988-01-01	2.48617253683763
1989-01-01	2.23436185838693
1990-01-01	2.05018605172514
1991-01-01	2.03035306840627
1992-01-01	2.11396450244610
1993-01-01	2.42785273923575
1994-01-01	2.86231137666417
1995-01-01	3.13518832605181
1996-01-01	3.38540963923343
1997-01-01	3.39478808943175
1998-01-01	4.21491204178731
1999-01-01	4.86997397930672
2000-01-01	4.94982546227464
2001-01-01	5.28978520827348
2002-01-01	5.61444317446031
2003-01-01	5.54848792748958
2004-01-01	5.00117771284961
2005-01-01	4.63162762392651
2006-01-01	4.37608661519456
2007-01-01	3.99266116029129
2008-01-01	4.14792632970465
2009-01-01	5.35252120961446
2010-01-01	5.50455819919922
2011-01-01	4.92546127181040
2012-01-01	4.64494886490810
2013-01-01	4.37133959175837
2014-01-01	3.80505381416894
2015-01-01	3.61532139875126
2016-01-01	3.40154729284226
2017-01-01	3.02138906963776