Period	Percent
1970-01-01	6.53
1975-01-01	8.31
1980-01-01	10.21
1985-01-01	11.08
1990-01-01	11.66
1995-01-01	11.02
2000-01-01	10.65
2005-01-01	9.60
2010-01-01	8.73