Year years 1960 66.75193691642491 1961 67.21766854303242 1962 67.04166644646865 1963 66.76696115174455 1964 66.96999166116359 1965 66.9831813905081 1966 66.89476294640573 1967 67.18204048988022 1968 66.29574578668617 1969 67.02631616513249 1970 67.31324973500257 1971 67.61455140875293 1972 67.60421854802202 1973 67.80312035533287 1974 68.3517301008228 1975 68.91762390022872 1976 69.21874415088281 1977 69.61281817458438 1978 69.7306678577722 1979 70.13058109009623 1980 70.15759827602487 1981 70.55985283197133 1982 70.95196558741813 1983 71.16695623442354 1984 71.29005509512659 1985 71.29069009722396 1986 71.40042916703923 1987 71.61214941238482 1988 71.62092342585304 1989 71.9233463889948 1990 72.05216965220777 1991 72.25486515591118 1992 72.54709050305571 1993 72.45026641554419 1994 72.65383632795199 1995 72.75663578769287 1996 73.3326881749611 1997 73.81004710714166 1998 74.01567254046377 1999 74.12753847897186 2000 74.35060976291344 2001 74.55877599831683 2002 74.67359445133704 2003 74.7793304337233 2004 75.26540347965904 2005 75.2787669799438 2006 75.50548338384247 2007 75.77600353119647 2008 75.88827033607224 2009 76.28917686951371 2010 76.49968089816903 2011 76.60846026951032 2012 76.7212045426426 2013 76.73500874370495 2014 76.82761769923127 2015 76.65567784195778 2016 76.48499272182934 2017 76.4700921996714 2018 76.56770628734144 2019 76.69988245053676 2020 74.7450957395982 2021 74.09782003956732 2022 75.25396310700584