Year	Number
1970	21.23169
1972	23.00061
1977	44.69118
1978	37.79049
1979	38.41701
1980	41.90828
1981	44.84531
1982	28.78324
1983	32.33508
1984	31.2264
1985	36.15916
1986	28.45799
1989	21.63038
1990	22.10538
1999	29.79998
2000	30.88668
2001	32.71757
2002	31.44496
2004	40.6197
2005	40.16487
2006	31.85068
2007	28.44015
2008	22.34335
2010	23.19708