Year	% of total
1990	41.04649134686031
1991	39.98950959004339
1992	39.06455733552661
1993	38.34337533055395
1994	37.360620033086676
1995	37.05122171103718
1996	37.66607029278012
1997	38.76395136117142
1998	39.014586433052536
1999	39.69770720459947
2000	40.44326917642406
2001	41.72407145315563
2002	42.319387514075686
2003	43.692933525661026
2004	44.27193211351845
2005	44.73841587880636
2006	45.752879217950564
2007	46.79677788296883
2008	47.4548121780784