Year	% of total
1990	17.171388924620477
1991	18.348597872121182
1992	18.284464915354373
1993	18.66078489061167
1994	18.761987150114408
1995	18.881285026882868
1996	20.854135559559904
1997	21.586800457194222
1998	21.73895742316215
1999	20.921241349338732
2000	20.72668796786124
2001	20.51569581481131
2002	19.48924705392384
2003	18.644635500161954
2004	18.58840958843357
2005	17.95040946883486
2006	17.859479935666997
2007	17.891247838518204
2008	18.54153807436464