Year	Number
1979	14.067404656353816
1980	12.201656703456363
1981	7.306403600029505
1982	8.47203887197506
1983	6.574214392033226
1984	4.448785153352913
1985	6.759329312262724
1986	5.631435526503166
1987	8.359290522029147
1988	9.132613574515274
1989	10.299287553532862
2008	9.425137287790392
2009	12.205605022834394
2010	10.457387273104416
2011	10.343972875042539
2012	8.677208853618145
2013	8.588137666281769
2014	10.702694846181487
2015	9.770193960431184
2016	11.8280603760738
2017	12.13427664183126
2018	12.178586861258047
2019	13.748909105863335
2020	16.631633655194094