Year	Number
1979	7.018155471073711
1980	5.623135270045644
1981	3.757085830788744
1982	4.6090034203007875
1983	4.054668303385557
1984	4.031524327261575
1985	4.478466658235535
1986	4.359386131936731
1987	4.184354914055757
1988	4.052616919197996
1989	4.691993012869773
1991	2.7706161996786696
1992	2.648817380500393
1993	3.377831069196926
1994	4.297576618036846
1995	4.386934847592299
1996	4.821690373170425
1997	4.139809990188267
1998	3.645525952388885
1999	4.117067718619696
2000	4.003125458192881
2001	4.297215758259685
2002	4.650986194667078
2003	4.861943322843979
2004	4.595424068682543
2005	3.9029923726839226
2006	4.501376145723593
2007	5.464694218932477
2008	6.222248591353978
2009	7.6174730585026955
2010	7.211137329226289
2011	6.738205251264457
2012	6.689415586821536
2013	6.414214498996065
2014	6.320105514383784
2015	5.958247977413683
2016	5.90994609894701
2017	6.082328378229773
2018	5.388943515044695
2019	5.475195988746099
2020	7.169474207240146
2021	4.759579154030254
2022	3.944413010930758
2023	4.140500552623795