Period	Percent
1970-01-01	2.70
1975-01-01	3.40
1980-01-01	3.51
1985-01-01	4.60
1990-01-01	4.57
1995-01-01	4.23
2000-01-01	4.50
2005-01-01	7.50
2010-01-01	10.08