Year	Number
1977	3.4579448957889305
1978	3.6598113077280328
1979	5.489144578811114
1980	5.8249665277864136
1981	4.641484532912077
1982	4.010943736014728
1983	3.454303504496919
1984	2.7949157204669497
1985	4.248095895789631
1986	3.9145107591836874
1987	5.170503740759865
1988	3.6146169475002305
1989	3.1480657186674192
1990	2.606248739968647
1991	3.901196468502584
2005	22.789434324143297
2006	30.16300304556902
2007	35.395039007807945
2008	32.07382017144181
2009	33.79143408272884
2010	36.78194147732532
2011	34.823817714375444
2012	34.307397119989346
2013	32.781290497834725
2014	28.192250442347536
2015	25.856906552358513
2016	22.579256610452482
2017	19.37160832351737
2018	15.926933826264028
2019	14.466575233627182
2020	15.441456289134614
2021	13.766216106668011
2022	16.33006020081457
2023	16.91419651830749