Year	Percent of Total
1960-01-01	62.7532460532977
1961-01-01	62.2748842366906
1962-01-01	61.8232808594437
1963-01-01	61.4351435835176
1964-01-01	61.1472037789388
1965-01-01	60.9804688116562
1966-01-01	60.8446837563169
1967-01-01	60.8472371839939
1968-01-01	60.9762034090921
1969-01-01	61.1995706311722
1970-01-01	61.4998720647560
1971-01-01	61.8914093622620
1972-01-01	62.2839440498169
1973-01-01	62.6869286792641
1974-01-01	63.1075034659673
1975-01-01	63.5391892554588
1976-01-01	63.8550959056802
1977-01-01	64.1908336587350
1978-01-01	64.5424145812906
1979-01-01	64.8956396699831
1980-01-01	65.2317999576708
1981-01-01	65.5278670025588
1982-01-01	65.8015099358688
1983-01-01	66.0267953359217
1984-01-01	66.1901107580996
1985-01-01	66.2894005707826
1986-01-01	66.2437870550499
1987-01-01	66.1879123626772
1988-01-01	66.1095922640580
1989-01-01	65.9905209522210
1990-01-01	65.8299281454214
1991-01-01	65.4751781395507
1992-01-01	65.0689701903669
1993-01-01	64.6635671211463
1994-01-01	64.3380528984426
1995-01-01	64.1449576011128
1996-01-01	64.1481884985460
1997-01-01	64.2765743514773
1998-01-01	64.4968090349263
1999-01-01	64.7451829172610
2000-01-01	64.9812084092977
2001-01-01	65.1707068376482
2002-01-01	65.3213921226064
2003-01-01	65.4981937427633
2004-01-01	65.7800040544156
2005-01-01	66.1942692230796
2006-01-01	66.4779485709960
2007-01-01	66.8408291927977
2008-01-01	67.2137216928686
2009-01-01	67.5054154958747
2010-01-01	67.6698818738079
2011-01-01	67.6027795944435
2012-01-01	67.4743087343609
2013-01-01	67.2791287992071
2014-01-01	67.0127539045965
2015-01-01	66.6707326084822
2016-01-01	66.3218699726525
2017-01-01	65.9534705619365