Year	Number
1960	10.44039649659472
1961	11.628490588259803
1962	14.015723618456468
1963	8.564501085291289
1964	6.881555132306553
1965	8.299723570324325
1966	9.208538031838978
1967	11.169366754638629
1968	13.273355565447181
1969	15.487610627922415
1970	14.861108276064712
1971	10.89137738614756
1972	10.68954911320506
1973	8.6899726702193
1974	11.34776376294852
1975	17.285262936688998
1976	17.87099701323408
1977	11.201288487094322
1978	6.917924935951472
1979	7.013889564112677
1980	6.856866394032735
1981	8.18125150828358
1982	8.246553432318317
1983	6.812978479315216
1984	8.519262184515197
1985	5.804669017043116
1986	8.852527587935546
1987	5.755124835198919
1988	5.859250068225327
1989	8.860931658493357
1990	7.005964064675298
1991	9.897462463027262
1992	7.173041324140908
1993	8.47235221068475
1994	8.790421938352628
1995	8.806132731862002
1996	7.266558886085612
1997	5.126453775177488
1998	6.448004234721869
1999	4.255192967707971
2000	5.083196352696042
2001	4.533350521673795
2002	3.1815714214402524
2003	2.720927209544689
2004	2.9181117336252576
2005	3.9230316899085738
2006	4.82792066771989
2007	5.59703484412703
2008	5.184901200637695
2009	2.847291099261762
2010	2.9319952582207627
2011	2.6019267483551194
2012	2.3308528395402646
2013	2.2037171316139252
2014	2.9596171638171285
2015	3.1385429593979617
2016	2.9547006327477208
2017	2.703510525663118
2018	3.0433764823752867
2019	3.236137158295408
2020	3.3257657354385683
2021	3.032505429773006
2022	2.5577552683648714
2023	2.435145405578945