Year	Percent
1975-01-01	16032500000
1976-01-01	16830250000
1977-01-01	16726000000
1978-01-01	16996500000
1979-01-01	17887250000
1980-01-01	18321500000
1981-01-01	18834000000
1982-01-01	18355500000
1983-01-01	17214750000
1984-01-01	18184000000
1985-01-01	18847000000
1986-01-01	18778750000
1987-01-01	19896750000
1988-01-01	21136250000
1989-01-01	21585250000
1990-01-01	21319000000
1991-01-01	20566750000
1992-01-01	20342750000
1993-01-01	21223750000
1994-01-01	22189250000
1995-01-01	22239500000
1996-01-01	22952750000
1997-01-01	23348750000
1998-01-01	24153500000
1999-01-01	24342000000
2000-01-01	25309750000
2001-01-01	25312750000
2002-01-01	26463250000
2003-01-01	27174250000
2004-01-01	27261750000
2005-01-01	26963750000
2006-01-01	27118000000
2007-01-01	27647500000
2008-01-01	28531000000
2009-01-01	26462000000
2010-01-01	27307500000
2011-01-01	27356000000
2012-01-01	26840000000
2013-01-01	26264250000
2014-01-01	25895000000
2015-01-01	25537000000
2016-01-01	24866000000
2017-01-01	25074250000