Year	Number
1970	19.97098
1971	27.11151
1972	27.36527
1973	32.41194
1974	24.31632
1975	17.30678
1976	21.35459
1977	23.02387
1978	14.12186
1980	15.10251
1981	14.57403
1983	12.82532
1984	15.96088
1985	13.87431
1986	17.35353
1987	16.77208
1988	15.48261
1989	15.49985
1990	15.99609
1991	16.58885
1992	16.93132
1993	16.90628
1994	14.92627
1995	16.17822
1996	16.26431
1998	16.17516
1999	14.38677
2000	14.82016
2001	14.10194
2002	13.92717
2003	12.52538
2004	11.70518
2005	11.04383
2006	11.34958
2007	10.86575
2008	9.974
2009	10.00659
2010	9.20384
2011	9.94465
2012	10.13979
2014	9.91343
2015	10.56204
2016	11.53695