Year	% of total
1990	12.271485379120046
1991	12.62364414315223
1992	13.170655308773785
1993	13.55717043333472
1994	13.700653978084476
1995	14.13701629942743
1996	14.321541632496098
1997	14.73852997074286
1998	15.377769847649711
1999	15.420437032601887
2000	15.356831833057246
2001	15.156150949616617
2002	15.161844593550738
2003	15.868128441108343
2004	15.121644784614281
2005	15.527211451828592
2006	15.021148405640691
2007	14.64136315536172
2008	15.122190060455313