Year	Number
1975	10.926389689573764
1976	7.898574257450844
1977	6.835427849958513
1978	7.696585896425568
1979	9.017232870623035
1980	7.344800134329379
1981	5.874377043976302
1982	5.43365385326918
1983	6.28694274112377
1984	5.836116989473443
1985	6.689325393875631
1986	5.6598932060570455
1987	5.986771368985209
1988	4.186852074944112
1989	4.379287605291275
1990	5.90902775475345
1991	6.072233182519979
1992	6.2903281629544985
1993	6.661348337464048
1994	7.278565550661637
1995	6.4152022562704705
1996	7.292518771194705
1997	6.14862097040808
1998	5.267642157854742
1999	5.573562174701637
2000	4.921661873300026
2001	4.588191353232842
2002	5.103398143249879
2003	6.284283778507489
2004	5.598635515505182
2005	5.414247273008935
2006	5.662600251421743
2007	7.520650819777781
2008	6.448633088520997
2009	9.335508446797677
2010	7.954514731181226
2011	7.794515412777145
2012	8.494105840478566
2013	8.263208386060422
2014	8.37588519062163
2015	10.064630708229382
2016	11.045696602881936
2017	10.146571779967825
2018	9.09542463718583
2019	8.731886563458023
2020	10.972623253871161
2021	8.133637720654889
2022	6.2029260635021
2023	6.915946017829598