Period	Percent
1970-01-01	5.25
1975-01-01	7.76
1980-01-01	9.10
1985-01-01	10.26
1990-01-01	11.04
1995-01-01	13.85
2000-01-01	16.42
2005-01-01	21.84
2010-01-01	31.92