Period	Percent
1970-01-01	4.40
1975-01-01	5.33
1980-01-01	6.71
1985-01-01	8.72
1990-01-01	9.37
1995-01-01	9.67
2000-01-01	10.01
2005-01-01	9.98
2010-01-01	11.15