Year Number 1975 87.795992714 1976 88.4942319369 1977 89.1924711597 1978 89.8907103825 1979 90.5889496053 1980 91.2871888282 1981 91.985428051 1982 92.6836672738 1983 93.3819064967 1984 94.0801457195 1985 94.7783849423 1986 95.4766241651 1987 96.174863388 1988 96.8731026108 1989 97.5713418336 1990 98.2240437158 1991 98.9222829387 1992 99.6205221615 1993 99.9544626594 1994 103.2391360916 1995 106.5238095238 1996 109.8128545407 1997 113.1018995576 1998 116.3909445746 1999 119.6799895915 2000 103.8797814208 2001 106.9344262295 2002 109.9890710383 2003 113.043715847 2004 116.0983606557 2005 119.1530054645 2006 122.2076502732 2007 125.262295082 2008 128.3169398907 2009 131.3715846995 2010 134.4262295082 2011 130.5100182149 2012 131.693989071 2013 132.9690346084 2014 110.5646630237 2015 110.9289617486 2016 110.4735883424 2017 141.1657559199 2018 141.1657559199 2019 141.1657559199 2020 141.1657559199