Year	Number
1961	11.920464545580225
1962	12.786712087678264
1963	13.665569219051742
1964	14.494598451673653
1965	15.2394089507803
1966	16.730463884556258
1967	18.128786959945966
1968	19.491224405692705
1969	20.95685974070806
1970	21.270821406369823
1971	23.191258638196818
1972	25.392495322147465
1973	27.61410472837598
1974	30.10531909413323
1975	34.04793222326759
1976	36.55020737654706
1977	40.154592668170594
1978	44.65484860944912
1979	49.094360946972586
1980	52.02653721376716
1981	56.039178015064515
1982	57.565363014761125
1983	59.72209186357403
1984	61.48302233699498
1985	62.19799244690958
1986	64.94255369824862
1987	67.42344977637028
1988	70.16412677197903
1989	73.39819204182355
1990	75.4407638366661
1991	76.89019623626292
1992	87.41588498625639
1993	87.76308078345286
1994	87.79448737317705
1995	88.41093065952165
1996	89.4679729280559
1997	90.9625848303262
1998	92.67890653295767