Year	Number
1977	5.663130452660279
1978	6.619470152163081
1979	8.527056539299322
1980	7.152721248857891
1981	4.1288556392284645
1982	5.71828767795029
1983	5.660923896955576
1984	5.131175085695107
1985	4.73865274371546
1986	5.232942785742773
1987	5.796477553188383
1988	4.578420126828371
1989	4.42226399880224
1990	5.522435657061537
1991	6.353836906984265
1992	5.383465688454478
1993	5.679781076354704
1994	6.0446345705246625
1995	5.82560476391531
1996	6.546742285112834
1997	8.96760749954843
1998	9.29997060699215
1999	8.91489052543235
2000	7.863128997286187
2001	8.988033411940993
2002	10.529459681724168
2003	9.178401648684225
2004	10.247970957334648
2005	11.8589151366121
2006	13.568042592430166
2007	15.962072316359938
2008	16.515199352976865
2009	21.557556762957446
2010	18.831788656308085
2011	17.733806089291832
2012	16.87958415252409
2013	17.085218439117515
2014	16.423733953469462
2015	15.984888324874905
2016	15.441307013400957
2017	14.124960622845293
2018	12.198542346956263
2019	12.301649722053218
2020	13.948786713897736
2021	10.758132229885096
2022	9.634479307674432
2023	10.249536444355995