Year	Number
1974	8.72917
1975	5.23913
1976	6.62981
1977	7.98452
1978	8.02131
1979	9.13704
1981	8.56793
1982	10.41
1983	11.15455
1984	10.82791
1985	12.48274
1986	12.09537
1987	12.87989
1988	13.30302
1989	13.74661
1990	15.28029
1991	14.62237
1992	16.55477
1993	16.53314
1994	17.31687
1995	17.20307
1996	17.04004
1997	17.23655
1998	17.46912
1999	17.8068
2000	17.92822
2001	17.64637
2002	17.52613
2003	17.37277
2017	9.97437
2018	10.21867