Year	% of total
1990	53.56540122846192
1991	52.543590796574364
1992	51.92158173711204
1993	50.997163069911245
1994	50.92327227748897
1995	50.76467513809489
1996	51.08633085900973
1997	51.64088349218133
1998	51.93026795295355
1999	52.187152746131524
2000	52.93356556091563
2001	53.11457135486856
2002	53.74878874158207
2003	53.67004344677604
2004	54.714598193715275
2005	55.38463000783673
2006	56.04246246635564
2007	56.853386738220244
2008	57.338202642891886