Year	Number
1975	4.048796256883439
1976	3.5804763895467677
1977	4.472875378217754
1978	5.222744380131987
1979	6.792527213991699
1980	6.2939866388379855
1981	4.68004601277035
1982	5.370707835799985
1983	4.852242134170113
1984	4.16823980317522
1985	4.4304349319219645
1986	4.318323916364742
1987	4.716012992903352
1988	3.7417880428872876
1989	3.7016201432159654
1990	3.4977396873813795
1991	3.5885657942766325
1992	3.159858457954359
1993	3.4898929819880515
1994	3.3844092258904346
1995	3.0719583229944014
1996	3.558844918285259
1997	3.6204285012678175
1998	3.700041832840441
1999	4.3044131248496305
2000	4.465431091375445
2001	5.29896404365881
2002	6.2883967262842795
2003	8.314689484025848
2004	9.090576729817966
2005	7.9906097115136125
2006	7.403643748007241
2007	7.113772278452395
2008	6.334815986762671
2009	8.345024833109425
2010	7.277549310071334
2011	7.089622452534247
2012	7.345024349907169
2013	7.705998792579097
2014	7.502826174970698
2015	8.933642239807448
2016	9.171571997444298
2017	9.264060835038036
2018	8.353293289738355
2019	8.895192262793692
2020	11.272315112815267
2021	9.594574315338916
2022	7.174532459401962
2023	7.094331976495302