Year	Number
1960	1.426951899226947
1961	1.8795786916509272
1962	2.315721532022241
1963	2.3852841288590105
1964	2.9922023445957278
1965	3.4506282833547366
1966	3.3304526168119937
1967	4.057570786874581
1968	4.003575848593813
1969	5.205681346988848
1970	4.6659143996669785
1971	3.80131510900637
1972	3.6024808237857253
1973	2.4969380799118954
1974	1.77535006096307
1975	1.8512509032301594
1976	1.947412712792097
1977	1.4833206331122435
1978	1.2286167138442166
1979	0.9708849800804618
1980	1.1179337752664884
1981	1.6714720417289453
1982	1.816203891875566
1984	3.0762278905178615
1985	2.926295278390253
1986	3.1579338334401226
1987	4.050851926620842
1988	6.19464026378841
1989	8.851430092364438
1990	12.302886490637263
2008	0.9806755226472471
2009	0.9622611278731019
2010	1.0858083634571811
2011	1.027793178790376
2012	0.9161015664087787
2013	0.9033507868958875
2014	0.9313858770198511
2015	0.9304715906053032
2016	0.9260617618672522
2017	0.8537138132641914
2018	0.8052989388154177
2019	0.7734060130779912
2020	0.7677863106615477