Year	Number
1975	6.4928798649520365
1976	5.38467702046135
1977	5.485868569505894
1978	5.528752341399822
1979	6.974065933726126
1980	6.327242319827912
1981	4.670377599689934
1982	5.353477776142653
1983	5.087814057279619
1984	4.587711238879672
1985	5.049172929582814
1986	5.6188198743843465
1987	6.426764484261577
1988	5.018686583559634
1989	4.713333666802635
1990	4.567549491369726
1991	4.838163197855103
1992	4.327188752967778
1993	4.622052775887441
1994	4.727178310085717
1995	4.252583154721138
1996	4.670851771032305
1997	5.247789251280214
1998	5.481434240771308
1999	5.7813137670932075
2000	5.514908957218887
2001	6.5668436871974905
2002	7.8401714363445905
2003	8.995789487751322
2004	9.567222131029045
2005	9.934450169325796
2006	10.650044785789351
2007	11.943771499265255
2008	12.13691708848002
2009	15.511492522891078
2010	13.758580706034213
2011	13.207108911855519
2012	13.116796408201393
2013	13.683370716155283
2014	13.064832977907614
2015	13.124887210364085
2016	12.979925281380282
2017	12.126911987948803
2018	10.830997048462592
2019	11.15012206880321
2020	13.396255016811926
2021	10.80990126513029
2022	9.129830400657182
2023	9.400723954260785