Year	Number
1961	24.084431811499964
1962	25.803166465576556
1963	27.649987813004554
1964	29.402756674471682
1965	31.08627049917549
1966	33.83774288183484
1967	36.252160789915855
1968	38.82771884839811
1992	108.8194817806583
1993	108.26922289595204
1994	106.69700761151404
1995	105.48450075504022
1996	104.20755415903798
1997	103.02350926654535
1998	104.08922281836556
1999	105.24221193201649