Year	Number
1970	8.79834
1971	8.02698
1972	9.15808
1974	9.30132
1975	8.87196
1976	7.55947
1981	11.53427
1982	11.425
1988	9.56469
1989	11.40678
1990	11.30418
1991	10.51433
1992	9.23464
1993	12.31343
1994	13.59586
1995	16.82379
1996	13.34344
1999	18.30072
2000	16.58745
2001	15.40768
2002	22.91717
2003	24.93085
2004	21.19962
2006	23.58161
2008	30.08322
2009	31.45138
2010	22.59288
2011	24.47362