Year	% of total
1970	33.80206504343167
1971	34.17494484352809
1972	35.078250248457195
1973	35.73467725204032
1974	36.46270743407672
1975	37.11601061531264
1976	37.08866439701086
1977	36.27657394366467
1978	37.48401337701173
1979	37.094292095119755
1980	36.6819649366011
1981	38.045448278453605
1982	37.31700559407284
1983	38.460411676926846
1984	38.775253073174056
1985	39.70501960673925
1986	37.21547591951138
1987	36.76681183656799
1988	37.224520268585756
1989	36.344400850597125
1990	64.81481481481481
1991	65.35714285714286
1992	65.03496503496503
1993	64.3598615916955
1994	65.47231270358306
1995	62.671232876712324
1996	66.97247706422019
1997	68.15476190476191
1998	69.71428571428572
1999	68.73156342182891
2000	71.46739130434783
2001	66.26506024096386
2002	67.21763085399449
2003	65.09695290858726
2004	63.18681318681318
2005	65.27093596059113
2006	62.189054726368155
2007	61.1904761904762
2008	58.57142857142858