Year	% of total
1990	16.527668096776196
1991	18.918316624570675
1992	19.864829109487786
1993	21.231205155982654
1994	21.55555586851006
1995	20.901265905653425
1996	20.50229426074097
1997	19.19218189583725
1998	19.598453696480092
1999	19.289246317304265
2000	19.50152732259791
2001	19.358764093349258
2002	19.88335016385479
2003	19.680197446242644
2004	21.52694736641714
2005	22.098072130087388
2006	23.722378368700195
2007	23.207185756978674
2008	21.929747978126834
2009	23.312242403025344
2010	23.523648508990444
2011	22.896383182070306
2012	21.886304645235004
2013	21.262310735305118
2014	21.184506569672838
2015	23.735413377799215
2016	22.399013093704284