Year	Number
1972	7.60057
1973	8.33333
1974	7.90762
1975	4.94194
1976	4.96154
1977	4.58228
1978	4.61945
1979	3.77434
1982	4.80197
1983	3.972
1984	4.44963
1985	3.92494
1986	3.65081
1987	4.56123
1989	4.35655
1995	7.74303
1996	8.62725
1997	9.77607
1999	9.14099
2001	10.01825
2003	13.80569
2004	17.06995
2005	18.84973
2010	18.92662
2012	34.44989