Period	Percent
1970-01-01	0.18
1975-01-01	0.20
1980-01-01	0.33
1985-01-01	0.36
1990-01-01	0.50
1995-01-01	0.61
2000-01-01	0.74
2005-01-01	1.06
2010-01-01	1.91