Year	Number
1975	49.1888207226
1976	50.2358554874
1977	51.2828902522
1978	52.329925017
1979	53.3769597819
1980	54.4239945467
1981	55.8773006135
1982	57.3306066803
1983	58.7839127471
1984	60.2372188139
1985	61.6905248807
1986	62.5112474438
1987	60.0430811179
1988	57.5749147921
1989	55.1067484663
1990	52.6385821404
1991	50.1704158146
1992	49.6478073165
1993	49.1251988185
1994	48.6025903204
1995	48.0799818223
1996	47.5573733242
1997	47.0347648262
1998	47.7641445126
1999	48.493524199
2000	49.2229038855
2001	48.815269257
2002	48.4076346285
2003	49.2847080209
2004	50.1617814133
2005	51.0388548057
2006	49.3612815269
2007	47.6837082481
2008	47.4164962509
2009	49.2433537832
2010	47.7300613497
2011	47.8118609407
2012	50.1022494888
2013	44.1036128153
2014	44.7975460123
2015	42.9584185412
2016	42.5644171779
2017	41.0279481936
2018	40.0940695297
2019	39.8289025222
2020	43.2540392297