Year	Percent
1987	45.12106
1988	45.63994
1989	46.95873
1990	42.60755
1991	54.54515
1992	52.15181
1993	37.46063
1994	42.62919
1995	38.16382
1996	33.78108
1997	30.48037
1998	30.62879
1999	32.01806
2000	30.80555
2001	30.67143
2002	30.76923
2003	31.0813
2004	32.54354
2005	28.48622
2006	31.4724
2007	32.3509
2008	29.2237
2009	25.8266
2010	25.89837
2011	25.10925
2012	24.54222
2013	22.56842
2014	22.81899
2015	21.78855
2016	22.98691
2017	23.98552