Year	Number
1960	3.9824701627023167
1961	3.7454672052022393
1962	4.036607355306521
1963	4.106775946459907
1964	4.316025560730799
1965	4.450331822054848
1966	4.637514812665501
1967	4.796413185461626
1968	4.1464795325400035
1969	5.131384255311532
1970	4.725226947605275
1971	3.968172134085633
1972	3.604987890320661
1973	3.1235481529343407
1974	1.8835863350445539
1975	2.6221448177163915
1976	2.6485696194166013
1977	2.5491360972025556
1978	2.5043589431165776
1979	1.8265419911354477
1980	1.6614530516176536
1981	2.1125860416191515
1982	2.1324530103976467
1983	2.44973082084423
1984	2.8442122531379486
1985	2.565494771464962
1986	3.0151830750664685
1987	3.22377772603389
1988	4.022640182381609
1989	3.8045423131912464
1990	4.32486325659259
1991	4.495251777242632
1992	4.506128558604616
1993	4.371813766744804
1994	4.810318914071501
1995	5.652453504087058
1996	5.876983668125322
1997	5.842319761443755
1998	5.96137273501396
1999	7.020162771950063
2000	5.852048623909736
2001	6.3298266433743136
2002	6.096311570823492
2003	6.73456014290669
2004	6.997876085704646
2005	9.674225801345095
2006	8.976825561642901
2007	8.30781411877228
2008	9.710221045870432
2009	5.730804910420644
2010	3.1383127822470036
2011	3.3540988914484022
2012	2.2335356244081526
2013	2.329971574653125
2014	2.421904332744334
2015	2.090538731871974
2016	1.8715503775389644