Period	Percent
1970-01-01	0.86
1975-01-01	1.20
1980-01-01	2.20
1985-01-01	2.45
1990-01-01	2.75
1995-01-01	3.18
2000-01-01	3.60
2005-01-01	3.41
2010-01-01	0.02