Year	years
1960	31.87
1961	32.409
1962	32.883
1963	33.346
1964	33.828
1965	34.289
1966	34.768
1967	35.225
1968	35.712
1969	36.206
1970	36.692
1971	37.178
1972	37.681
1973	38.241
1974	38.792
1975	39.35
1976	39.892
1977	40.492
1978	39.022
1979	37.314
1980	37.799
1981	38.312
1982	35.212
1983	35.518
1984	29.793
1985	29.896
1986	36.389
1987	36.739
1988	41.572
1989	42.891
1990	43.709
1991	44.353
1992	45.07
1993	50.216
1994	49.531
1995	51.039
1996	51.722
1997	52.153
1998	51.134
1999	53.41
2000	53.762
2001	54.272
2002	55.227
2003	56.032
2004	56.658
2005	57.013
2006	57.133
2007	57.342
2008	58.172
2009	58.82
2010	59.278
2011	59.825
2012	60.317
2013	60.791
2014	60.812
2015	60.76
2016	61.193
2017	60.105
2018	59.923
2019	60.619
2020	59.866
2021	58.915
2022	59.766