Year	Number
1980	9.2290688035
1981	9.3600442111
1982	9.4910196187
1983	9.6219950263
1984	9.7529704338
1985	9.8839458414
1986	10.0099474993
1987	10.1359491572
1988	10.2619508151
1989	10.3879524731
1990	10.513954131
1991	10.3161094225
1992	10.118264714
1993	9.9204200055
1994	9.722575297
1995	9.5247305886
1996	9.7941420282
1997	10.0635534678
1998	10.0967117988
1999	10.1298701299
2000	10.0469743023
2001	9.966841669
2002	9.8839458414
2003	9.8538961039
2004	9.8238463664
2005	9.7937966289
2006	9.7637468914
2007	9.7336971539
2008	9.7036474164
2009	9.6735976789
2010	9.6435479414
2011	9.6435479414
2012	9.6435479414
2013	9.6435479414
2014	9.6435479414
2015	9.6435479414
2016	9.6435479414
2017	9.6435479414
2018	9.6435479414
2019	9.6435479414
2020	9.6435479414