Year	Percent
1977-01-01	14.2030449793523
1978-01-01	13.9933733118235
1979-01-01	13.9003287493287
1980-01-01	14.2034095219940
1981-01-01	14.5492785524546
1982-01-01	14.8239626495334
1983-01-01	14.9453035124474
1984-01-01	14.7472429849342
1985-01-01	14.6141250378822
1986-01-01	14.5619143761195
1987-01-01	14.5603069941500
1988-01-01	14.5153655621547
1989-01-01	14.1242865459937
1990-01-01	14.4079464728870
1991-01-01	14.9069333842039
1992-01-01	14.8167479822171
1993-01-01	15.1211529415259
1994-01-01	15.7136359579909
1995-01-01	15.7093129376316
1996-01-01	15.7331899222022
1997-01-01	15.7670913855456
1998-01-01	15.7686109222573
1999-01-01	16.0147840471662
2000-01-01	16.0768472534046
2001-01-01	16.5520962760543
2002-01-01	17.0387974164838
2003-01-01	17.8307571081830
2004-01-01	18.0952413383577
2005-01-01	18.1875726831534
2006-01-01	18.0605027952031
2007-01-01	18.3134189611161
2008-01-01	18.5631620396861
2009-01-01	19.6425488941719
2010-01-01	20.4466476359026
2011-01-01	21.1035056986544
2012-01-01	21.1677041923125
2013-01-01	21.3414819078171
2014-01-01	21.5327783896153
2015-01-01	21.5255546641159
2016-01-01	21.2139588390536
2017-01-01	21.0317622889448