Year	% of total
1990	28.128836113859386
1991	27.893209610156493
1992	28.944039157447044
1993	28.67927838215515
1994	30.794659670521003
1995	30.69575665230535
1996	30.076916201115107
1997	30.251517283387912
1998	30.362012021010543
1999	29.641901794133247
2000	30.497635526308414
2001	30.312853724824606
2002	29.76964789849667
2003	30.049831773361856
2004	28.43117838639794
2005	28.712756691541326
2006	29.652697069162382
2007	29.78219727926396
2008	31.09997398631789
2009	29.49405832425495
2010	28.743816833828507
2011	29.79814214004856
2012	29.225128502833293
2013	28.82169966946475
2014	27.931461756077898
2015	27.61403986142344