Year	Percent
1976	18.69283
1977	17.65533
1988	19.20919
1989	21.00171
1990	26.6126
1991	29.09103
1994	27.87553
1995	22.03093
1996	22.63269
1997	23.25012
1999	28.79377
2000	31.55289
2001	34.30898
2002	37.68427
2003	43.5355
2004	44.30158
2005	39.82451
2006	38.76446
2009	39.44836
2010	38.59526
2011	41.89522
2012	42.56174
2013	46.26275