Period	Percent
1970-01-01	1.20
1975-01-01	2.07
1980-01-01	3.35
1985-01-01	3.73
1990-01-01	3.63
1995-01-01	2.75
2000-01-01	1.06
2005-01-01	1.10
2010-01-01	2.14