Year	% of total
1990	31.731503313598065
1991	33.8865439400893
1992	33.034858816085325
1993	35.05477463159719
1994	35.39837020400512
1995	32.93616115293248
1996	33.77704937996967
1997	33.27057758497278
1998	34.73530597312064
1999	34.94646858047478
2000	35.56515847114448
2001	33.98372564507238
2002	36.384862012124394
2003	37.3343224806883
2004	38.82106932417225
2005	40.61203962117648
2006	40.42251823827885
2007	39.74975288589417
2008	40.421968386737966
2009	40.07398668701674
2010	41.49183242150425
2011	43.50810895498208
2012	42.73287298812317
2013	42.377771411215036
2014	43.86469957580803
2015	46.85000217331312
2016	48.518508178696756