Year	Percent
1969	5.5
1975	5.4
1980	3.3
1985	9.1
1990	14.5
1991	11.8
1993	21.9
1995	17.8
1996	13
1997	23.9
1999	17
2001	27.6
2003	32.1
2006	26
2007	29.6
2008	27
2012	29
2013	35.4