Year	Number
1970	0.79125
1973	1.48814
1974	2.25756
1975	2.89743
1976	3.21721
1977	3.37327
1978	3.35311
1979	4.15178
1980	4.40629
1981	5.90136
1985	7.33916
1986	8.57496
1987	8.15753
1994	8.62926
1997	11.41202
1998	11.76455
1999	12.63359
2000	14.07175
2001	15.96658
2002	17.86136
2003	20.45389
2004	22.47211
2005	14.67141
2006	17.53158
2007	17.14973
2008	16.73773
2009	19.61024
2010	19.94105
2011	19.48791