Year Percent of Total 1960-01-01 1.94041259986390 1961-01-01 2.00199044180335 1962-01-01 2.06099162536544 1963-01-01 2.11630997760722 1964-01-01 2.16882646586708 1965-01-01 2.21782868636301 1966-01-01 2.27785595597143 1967-01-01 2.33235071073834 1968-01-01 2.38237403133862 1969-01-01 2.42886641548395 1970-01-01 2.47295692953657 1971-01-01 2.52452758095412 1972-01-01 2.57130682028111 1973-01-01 2.61357999288605 1974-01-01 2.65287149730010 1975-01-01 2.68874662636620 1976-01-01 2.73186683172914 1977-01-01 2.76993056877897 1978-01-01 2.80389446663730 1979-01-01 2.83402086269785 1980-01-01 2.86059768526516 1981-01-01 2.89745385822623 1982-01-01 2.92900726344574 1983-01-01 2.95653920846447 1984-01-01 2.98074397435629 1985-01-01 3.00281026157919 1986-01-01 3.03254917431979 1987-01-01 3.05706427333726 1988-01-01 3.07732389253885 1989-01-01 3.09443682535184 1990-01-01 3.10919443979233 1991-01-01 3.13082377630561 1992-01-01 3.14796784414262 1993-01-01 3.16139124125883 1994-01-01 3.17095183830569 1995-01-01 3.17690663171578 1996-01-01 3.18048426422831 1997-01-01 3.17931961427384 1998-01-01 3.17473206541758 1999-01-01 3.16817197789260 2000-01-01 3.16059997955236 2001-01-01 3.16075118723459 2002-01-01 3.15731992031262 2003-01-01 3.15141402927243 2004-01-01 3.14362682285496 2005-01-01 3.13471022640159 2006-01-01 3.13290503509692 2007-01-01 3.12817625688079 2008-01-01 3.12178195361406 2009-01-01 3.11420510808011 2010-01-01 3.10657055477660 2011-01-01 3.10363582370903 2012-01-01 3.09897110859140 2013-01-01 3.09522904487136 2014-01-01 3.09496742061852 2015-01-01 3.10020153784687 2016-01-01 3.11812226779800 2017-01-01 3.13824039904221