Year	Number
1988	2.4744427988296067
1989	2.2648341441143596
1990	3.837885065328501
1991	2.002895758744866
1992	1.205576980887533
1993	6.583198305955886
1994	3.6837310105402183
1995	4.557617045727263
1996	4.35273582729222
1997	3.145817177031273
1998	4.000252495677189
1999	2.938650708958951
2000	3.1235470395532623
2001	3.9557996005558542
2002	3.563395327326604
2003	3.3770943668540956
2004	2.853569766479912
2005	2.7392366688931635
2006	2.2329865246638736
2007	2.105309868195059
2008	2.0811457442927463
2009	1.6436256338828796
2010	1.6654649125894234
2011	1.6983021217533252
2012	1.8712988590430282
2013	1.9968882436439794
2014	1.9221152319090073
2015	1.988891743620192
2016	2.1415090580135647
2017	2.100317629737218
2018	1.984588423123709
2019	1.894237831257662
2020	1.576771066551871
2021	1.3909708865749244
2022	1.3948693178777727