Period	Percent
1970-01-01	0.50
1975-01-01	0.74
1980-01-01	1.31
1985-01-01	1.64
1990-01-01	2.30
1995-01-01	3.32
2000-01-01	4.57
2005-01-01	6.18
2010-01-01	7.92