Year	Percent
1974	12.99
1975	17.24
1976	19.08
1977	14.87
1978	13.79
1979	14.35
1980	12.41
1981	12.61
1982	12.78
1983	12.96
1984	13.11
1985	13.29
1986	13.38
1990	5.11
2000	5.05
2005	9.98
2010	9.2