Period	Percent
1970-01-01	6.77
1975-01-01	8.63
1980-01-01	10.54
1985-01-01	11.61
1990-01-01	12.40
1995-01-01	13.74
2000-01-01	16.62
2005-01-01	25.48
2010-01-01	22.83