Period	Percent
1970-01-01	1.50
1975-01-01	2.14
1980-01-01	3.49
1985-01-01	4.79
1990-01-01	6.35
1995-01-01	8.11
2000-01-01	9.08
2005-01-01	11.40
2010-01-01	14.27