Year	Number
1970	1.8298261665
1971	1.8693504117
1972	1.9088746569
1973	1.9483989021
1974	1.9879231473
1975	2.0274473925
1976	2.0669716377
1977	2.1064958829
1978	2.1460201281
1979	2.1855443733
1980	2.2250686185
1981	2.2645928637
1982	2.3041171089
1983	2.3436413541
1984	2.3831655993
1985	2.4226898445
1986	2.4622140897
1987	2.5017383349
1988	2.5412625801
1989	2.5807868253
1990	2.6203110704
1991	2.6598353156
1992	2.6993595608
1993	2.738883806
1994	2.7784080512
1995	2.8179322964
1996	2.8574565416
1997	2.8969807868
1998	2.936505032
1999	2.9760292772
2000	3.0155535224
2001	3.1617108875
2002	3.3078682525
2003	3.7278896005
2004	4.1479109485
2005	4.5679322964
2006	4.9879536444
2007	5.4079749924
2008	5.8279963403
2009	5.8279963403
2010	5.8279963403
2011	5.8279963403
2012	5.8279963403
2013	5.8279963403
2014	5.8279963403
2015	5.8279963403
2016	5.8279963403
2017	5.8279963403
2018	5.8279963403
2019	5.8279963403
2020	5.8279963403