Period	Percent
1970-01-01	0.40
1975-01-01	0.65
1980-01-01	1.13
1985-01-01	1.79
1990-01-01	2.49
1995-01-01	3.22
2000-01-01	4.18
2005-01-01	3.11
2010-01-01	3.13