Year	% of total
1990	37.614686281115176
1991	37.14656465108812
1992	36.72435987159864
1993	36.569640471460644
1994	36.79278699237955
1995	36.716464796916384
1996	36.51298599812628
1997	36.6378497646627
1998	37.021143736288664
1999	37.99738396205992
2000	38.25146619208406
2001	38.734026481423285
2002	39.05463796330038
2003	37.43373353234818
2004	38.51050351824754
2005	37.904423478909514
2006	38.585749799611
2007	38.72754524825669
2008	37.918092400626705