Year	Percent
1978-01-01	2.25099463309464
1979-01-01	2.10217621924034
1980-01-01	2.02689570654043
1981-01-01	2.21929810351364
1982-01-01	2.36775800525448
1983-01-01	2.67062854896149
1984-01-01	2.73458943253786
1985-01-01	2.63893254208736
1986-01-01	2.78992616448065
1987-01-01	2.87119632884689
1988-01-01	2.54184454887671
1989-01-01	2.28517483496770
1990-01-01	2.12464849676135
1991-01-01	2.11366184693777
1992-01-01	2.18339897018922
1993-01-01	2.52801030440600
1994-01-01	2.91868836056170
1995-01-01	3.18180206720263
1996-01-01	3.38898027234875
1997-01-01	3.42451552043012
1998-01-01	4.14461844634787
1999-01-01	4.72588451729170
2000-01-01	4.78537722363907
2001-01-01	5.09142206396863
2002-01-01	5.43066053165522
2003-01-01	5.31820740484767
2004-01-01	4.79024480957863
2005-01-01	4.49156183402283
2006-01-01	4.18845276637558
2007-01-01	3.90411958755641
2008-01-01	4.04927137846772
2009-01-01	5.14458306172732
2010-01-01	5.14124350637385
2011-01-01	4.62907989163468
2012-01-01	4.41704851120343
2013-01-01	4.09963902818863
2014-01-01	3.64899528600196
2015-01-01	3.41448391542771
2016-01-01	3.17119951117911
2017-01-01	2.87714716671660