5-years Percent 1970-01-01 0.18 1975-01-01 0.25 1980-01-01 0.30 1985-01-01 0.31 1990-01-01 0.34 1995-01-01 0.40 2000-01-01 0.49 2005-01-01 0.86 2010-01-01 1.42