Year	Number
1973	3.098300235010247
1974	2.5918827947622156
1975	2.5229055748675893
1976	2.8723606022511246
1977	1.8423263311369509
1978	2.8641640000861934
1979	3.0326919453752272
1980	2.687843534958416
1981	3.597409469229429
1982	3.4265790534702645
1983	4.612584412123475
1984	9.054157278906496
1985	6.432108559603994
1986	9.165645145622806
1987	6.270311384519503
1988	12.539398667711902
1989	10.088159738665619
1990	8.8257227294441
1991	5.986190782320963
1992	6.26487004393367
1993	6.718108676934387
1994	9.66895708415686
1995	13.069495714989069
1996	17.822575741679888
1997	16.930935279892356
1998	22.833042134810338
1999	19.00854611993421
2000	12.89984877301575
2001	16.695005778789994
2002	10.476549505771928
2003	11.599982810616996
2004	25.294027097196594
2005	15.813139287988164
2006	8.085840318309884
2007	16.977361441657095
2008	9.833216293151184
2009	2.4682291274913855
2010	2.3587264999237245
2011	2.197995865915071
2012	1.7578402590421145
2013	1.8308437550854928
2014	1.995016651982036
2015	1.7052675914660422
2016	1.957345464250185
2017	2.135208749131065
2018	2.238815723454109
2019	2.388357989412349
2020	2.510547499340353
2021	1.9761338048326333
2022	2.591582127705637