Year	Number
1970	36.42146
1971	36.31208
1972	36.17524
1973	36.26135
1974	36.446
1975	36.82616
1976	36.73622
1977	36.88287
1978	36.29664
1979	36.38641
1980	36.24235
1981	36.26762
1982	35.97623
1983	34.93737
1984	34.67502
1985	34.48125
1986	34.12903
1987	34.03938
1988	34.1622
1989	34.0081
1990	33.15345
1991	33.98974
1992	34.26106
1993	33.9115
1994	34.26673
1995	34.04304
1996	33.13055
1997	32.74651
1998	32.35435
1999	31.03909
2000	31.14166
2001	31.58165
2002	32.46654
2003	32.9414
2004	33.19695
2005	32.63663
2006	32.4006
2007	32.08582
2008	32.30469
2009	32.14036
2010	32.24411
2011	32.15943
2012	31.59612
2013	31.83551
2014	31.50363
2015	30.80537
2016	30.41004
2017	30.4998
2018	30.49175