Year	Number
1961	8.365639665374413
1962	8.551229508196721
1963	10.753086419753087
1964	10.805785123966942
1965	10.860995850622407
1966	10.927083333333334
1967	11.033613445378151
1968	12.896405919661733
1969	14.893617021276595
1970	14.582441113490363
1971	15.529715762273902
1972	16.193617021276594
1973	17.614736842105263
1974	19.552083333333332
1975	21.463917525773198
1976	20.884
1977	20.815686274509805
1978	21.009708737864077
1979	21.08076923076923
1980	20.14728385615914
1981	19.555555555555557
1982	18.763358778625953
1983	17.8212927756654
1984	16.420454545454547
1985	24.67289719626168
1986	32.77777777777778
1987	40.959409594095945
1988	49.080882352941174
1989	57.14285714285714
1990	65.23722627737226
1991	73.35520320758155
1992	77.82888684452622
1993	82.45125348189416
1994	86.97282099343954
1995	91.76915799432356
1996	96.4660936007641
1997	101.44648023143684
1998	106.5238558909445
1999	111.70108161258602
2000	116.80572109654351
2001	122.19101123595506
2002	127.56231003039514