Year	Number
1971	22.48383
1972	24.96949
1973	24.85004
1974	24.51026
1975	23.3296
1976	24.21889
1979	29.53634
1980	29.53633
1981	29.15275
1982	30.01593
1983	29.82095
1984	31.73373
1985	28.23134
1986	24.59649
1989	22.56667
1990	28.40339
1995	27.98683
1998	21.01898
1999	23.56028
2001	25.88448
2002	24.91811
2003	22.06977
2004	21.27358
2005	21.27349
2017	23.73181