Year	Number
1977	5.7080700966079645
1978	6.5106884882619465
1979	8.034295599945947
1980	6.710006882552329
1981	3.949436915797972
1982	5.24138897342085
1983	5.223467291317255
1984	4.827423793565757
1985	4.548882453559269
1986	5.011761391361407
1987	5.419493187557493
1988	4.256276122537573
1989	4.107418683344995
1990	5.0806543408014555
1991	5.862855356153064
1992	5.251415953029468
1993	5.661290954708066
1994	6.071506234366945
1995	5.801039650706463
1996	6.440299920091668
1997	8.538420343682011
1998	8.830808793689616
1999	8.287912870649205
2000	7.3981252726195805
2001	8.45978435210428
2002	10.043708670263268
2003	9.256616511516471
2004	9.98754241044523
2005	11.099587437834803
2006	12.609508626563668
2007	14.763919067517062
2008	15.069571774244793
2009	19.777409665879826
2010	17.42090007930098
2011	16.487972566941345
2012	15.72915283971697
2013	15.97182342060172
2014	15.333834533551439
2015	14.922944823116152
2016	14.418626661452391
2017	13.203909397322096
2018	11.391067082318258
2019	11.51574918978781
2020	13.471800686670909
2021	10.366295384196988
2022	9.080194733121717
2023	9.88445401558454