Year	Percent
1979-01-01	3.42949981481020
1980-01-01	2.93934431359920
1981-01-01	3.47942912295178
1982-01-01	3.77980570568593
1983-01-01	6.81478716168461
1984-01-01	6.36231856797551
1985-01-01	7.05304836739576
1986-01-01	6.10729879754654
1987-01-01	6.78532133906084
1988-01-01	6.83636688449468
1989-01-01	6.09969239332144
1990-01-01	6.46633161345083
1991-01-01	9.62508068612920
1992-01-01	11.80859757158500
1993-01-01	13.69876662040330
1994-01-01	11.50602090214830
1995-01-01	9.25022380310066
1996-01-01	9.02980389275842
1997-01-01	7.97485956796369
1998-01-01	7.25563516246512
1999-01-01	6.54237886037525
2000-01-01	5.32874941948406
2001-01-01	5.53983035059599
2002-01-01	5.13483108979636
2003-01-01	4.25562651134998
2004-01-01	3.88758147847752
2005-01-01	3.70190953763560
2006-01-01	3.54851293176653
2007-01-01	2.81871202221354
2008-01-01	3.05518657821528
2009-01-01	3.70339914428770
2010-01-01	3.73522446924076
2011-01-01	3.67039281542978
2012-01-01	3.72412506404174
2013-01-01	4.34191481336417
2014-01-01	4.31879987970860
2015-01-01	4.83088691568862
2016-01-01	4.81212612555401
2017-01-01	4.37371168556528