Year	Percent
1989	21.90227
1990	18.16206
1991	13.27136
1992	62.32246
1993	38.20459
1994	27.75838
1995	29.28946
1996	26.07331
1997	24.72999
1998	31.22148
1999	43.22027
2000	44.06072
2001	36.89342
2002	35.24933
2003	35.24998
2004	34.41789
2005	35.20307
2006	33.73048
2007	30.16407
2008	31.3096
2009	27.93811
2010	29.21559
2011	27.97692
2012	26.88344
2013	25.79297
2014	27.05302
2015	28.60643
2016	25.69898
2017	26.03959