Period	Percent
1970-01-01	1.40
1975-01-01	2.54
1980-01-01	3.76
1985-01-01	4.95
1990-01-01	5.90
1995-01-01	7.09
2000-01-01	10.10
2005-01-01	12.57
2010-01-01	18.13