Period	Percent
1970-01-01	2.60
1975-01-01	3.05
1980-01-01	4.10
1985-01-01	4.83
1990-01-01	5.97
1995-01-01	7.78
2000-01-01	9.40
2005-01-01	10.06
2010-01-01	12.13