Year	Percent
1960-01-01	53.7198331821343
1961-01-01	53.5611293483508
1962-01-01	52.6135034867852
1963-01-01	51.3174680546255
1964-01-01	50.4924520646432
1965-01-01	49.9961044349495
1966-01-01	50.1740090647566
1967-01-01	50.4435099804156
1968-01-01	50.1285884950632
1969-01-01	49.5985308390110
1970-01-01	49.3717609530574
1971-01-01	48.2956327393976
1972-01-01	47.2097292323979
1973-01-01	47.7719740495111
1974-01-01	46.0750411123337
1975-01-01	45.1041472919212
1976-01-01	45.1570109405479
1977-01-01	45.9523641348394
1978-01-01	46.5286248409560
1979-01-01	46.7897923417074
1980-01-01	46.8006796518055
1981-01-01	46.7886398895857
1982-01-01	47.0924654337670
1983-01-01	47.8568448972178
1984-01-01	47.7064799957778
1985-01-01	47.6077349234650
1986-01-01	47.4872401911235
1987-01-01	47.4784238600312
1988-01-01	47.8244096365475
1989-01-01	48.5316459709299
1990-01-01	49.1921159286312
1991-01-01	49.7380856748265
1992-01-01	49.7044186201759
1993-01-01	49.0587123637712
1994-01-01	48.7530911609508
1995-01-01	48.4165711305842
1996-01-01	48.3764224378601
1997-01-01	48.6661380797660
1998-01-01	48.1735611405330
1999-01-01	47.4584874485882
2000-01-01	47.1438536747495
2001-01-01	46.8809838372726
2002-01-01	46.0787353484207
2003-01-01	45.9808606865700
2004-01-01	46.1614332176880
2005-01-01	46.3682577327369
2006-01-01	46.6160278227819
2007-01-01	46.6693080181975
2008-01-01	46.5485727777154
2009-01-01	46.2067369761528
2010-01-01	46.2504484966545
2011-01-01	46.1671328148297
2012-01-01	46.2512444502804
2013-01-01	47.1271416654712
2014-01-01	47.6529133691160
2015-01-01	48.1236752344830
2016-01-01	48.9404476965858
2017-01-01	49.8090185841779