Year	Number
1961	17.70591942670412
1962	19.03208438133907
1963	20.530925042650765
1964	22.02883288891966
1965	23.625062154750527
1966	25.518098974333363
1967	27.560191198043157
1968	29.650715811963703
1969	31.73884401305269
1970	32.33872919117919
1971	35.17882804297309
1972	38.13362264571451
1973	41.279030928222284
1974	44.78740551180743
1975	50.362097967409014
1976	54.03442126194125
1977	58.359897782192306
1978	63.59227952759829
1979	69.46718216241342
1980	74.10247077998424
1981	79.2683236826659
1982	81.75243748693343
1992	113.13117861930414
1993	113.97080447908576
1994	116.49116699388865
1995	117.2087429559095
1996	118.21714675555758
1997	120.02768163814588
1998	121.55835586856413
1999	124.20684896535313
2000	130.5978156394485