Period	Percent
1970-01-01	0.57
1975-01-01	0.90
1980-01-01	1.30
1985-01-01	1.71
1990-01-01	2.41
1995-01-01	3.29
2000-01-01	4.21
2005-01-01	4.41
2010-01-01	4.58