Period	Percent
1970-01-01	4.00
1975-01-01	5.34
1980-01-01	6.10
1985-01-01	9.26
1990-01-01	12.00
1995-01-01	12.64
2000-01-01	11.08
2005-01-01	13.68
2010-01-01	11.74