Year % net 1981 97.10455 1982 97.81398 1990 95.91662 2000 87.15985 2001 87.40533 2004 92.37668 2005 90.16768 2006 92.50739 2007 91.79998 2016 93.97092 2017 95.17437 2018 96.08382