Year	Percent
1977-01-01	29.5857002259960
1978-01-01	28.5185090232914
1979-01-01	27.8113994592045
1980-01-01	27.5545902239792
1981-01-01	27.2942204473806
1982-01-01	27.0357915698481
1983-01-01	26.8435664180133
1984-01-01	26.2358231632175
1985-01-01	25.5639653493159
1986-01-01	24.9965651999673
1987-01-01	24.5080232743577
1988-01-01	24.1137021312501
1989-01-01	23.4151092959288
1990-01-01	23.4675092614289
1991-01-01	23.7503789586491
1992-01-01	23.3636452054027
1993-01-01	23.4122051094485
1994-01-01	23.2665284375319
1995-01-01	23.1261868425686
1996-01-01	22.9369022064925
1997-01-01	22.6334766640520
1998-01-01	22.6364264166161
1999-01-01	22.7691008017302
2000-01-01	22.8008749773289
2001-01-01	23.1880427461148
2002-01-01	23.5997210627330
2003-01-01	24.1798952530996
2004-01-01	24.5538001765498
2005-01-01	24.5912890847138
2006-01-01	24.4610592952301
2007-01-01	24.6977938238378
2008-01-01	24.7085712988387
2009-01-01	25.3755686426947
2010-01-01	26.0902121136363
2011-01-01	26.7069776495981
2012-01-01	26.8936441728237
2013-01-01	27.1889297009466
2014-01-01	27.3038644509182
2015-01-01	27.3938784440116
2016-01-01	27.0497594284142
2017-01-01	26.6595259677152