Year	Number
1977	5.666405190024661
1978	6.4574277111275675
1979	8.042478257690297
1980	6.7040706436464275
1981	3.9559078315716802
1982	5.2294754407866595
1983	5.201116905562395
1984	4.793091290895252
1985	4.535527107206309
1986	4.982921154887463
1987	5.401533067188668
1988	4.262029553630432
1989	4.122909742197482
1990	5.05782008350886
1991	5.839578637740224
1992	5.232402349011847
1993	5.646007497967701
1994	6.058450456173518
1995	5.790461386539075
1996	6.427468583144993
1997	8.512909971536232
1998	8.804422582598571
1999	8.265598769835321
2000	7.382281053992116
2001	8.442662123227159
2002	10.019667485000607
2003	9.237452780154847
2004	9.963016335068888
2005	11.128174107490198
2006	12.59271103756399
2007	14.708702411288344
2008	14.997336020433307
2009	19.677666030613583
2010	17.34223979617672
2011	16.440466391315976
2012	15.680147546842832
2013	15.924919846108306
2014	15.289177923797272
2015	14.88298049540447
2016	14.386492813361267
2017	13.176912054801814
2018	11.369353189191512
2019	11.500069372630866
2020	13.456476308233498
2021	10.353573102053264
2022	9.072330381035378
2023	9.878518682872697