Year	Number
1980	1.5209125475
1981	1.5408697719
1982	1.5608269962
1983	1.5807842205
1984	1.6007414449
1985	1.6206986692
1986	1.6406558935
1987	1.6606131179
1988	1.6805703422
1989	1.7005275665
1990	1.7204847909
1991	1.7404420152
1992	1.7603992395
1993	1.7803564639
1994	1.8003136882
1995	1.8202709125
1996	1.8402281369
1997	1.8220785805
1998	1.8039290241
1999	1.7857794677
2000	1.8299728408
2001	1.9537099402
2002	1.9422379142
2003	1.9609560022
2004	2.1363280826
2005	2.0830309614
2006	2.2349809886
2007	2.3011406844
2008	2.2313688213
2009	2.1615969582
2010	2.1335361217
2011	2.1054752852
2012	2.0774144487
2013	2.0941444867
2014	2.1131558935
2015	2.0634980989
2016	2.0138403042
2017	2.0464638783
2018	2.0464638783
2019	2.0464638783
2020	2.0464638783