Year	% of total
1990	29.501045488068538
1991	31.262824959721694
1992	31.640702457281392
1993	33.39872075307707
1994	35.48219868028769
1995	35.80963428919534
1996	37.24837485354292
1997	40.00344458139216
1998	39.99418531878266
1999	39.116082390396514
2000	38.461778160312264
2001	40.06930954973072
2002	40.88717449744308
2003	45.40767030872277
2004	47.33160443095945
2005	47.62117643058508
2006	47.118378470421305
2007	47.89153020260306
2008	46.21599090972328