Year	Number
1975	27.1690831069
1976	31.3840997385
1977	35.59911637
1978	39.8141330015
1979	44.0291496331
1980	48.2441662646
1981	50.275499581
1982	52.3068328974
1983	54.3381662138
1984	56.3694995303
1985	58.4008328467
1986	62.3365411472
1987	66.2722494477
1988	70.2079577483
1989	74.1436660488
1990	77.8762410177
1991	76.7691643603
1992	75.6620877028
1993	74.5550110454
1994	73.4479343879
1995	72.3408577305
1996	71.2134677399
1997	70.0860777493
1998	68.9586877587
1999	67.8312977681
2000	66.0183327832
2001	71.3251910723
2002	71.7060660691
2003	72.0869410659
2004	72.4678160628
2005	72.8486910596
2006	73.2295660564
2007	73.6104410532
2008	73.9913160501
2009	76.555874362
2010	79.120432674
2011	81.684990986
2012	84.2698626311
2013	86.8547342762
2014	89.4396059213
2015	92.0244775665
2016	94.6093492116
2017	89.5310159206
2018	95.9987812
2019	96.3105908641
2020	98.1133991824