Period	Percent
1970-01-01	2.22
1975-01-01	2.24
1980-01-01	2.60
1985-01-01	2.89
1990-01-01	5.01
1995-01-01	7.78
2000-01-01	9.08
2005-01-01	12.10
2010-01-01	6.23