US estate tax has fallen to zero after a failure to extend the law by the Senate last week, potentially increasing the federal deficit by $1.3 trillion, despite a number of US wealthy including Bill Gates Sr. lobbying for it to be reinstated.

US estate tax has been cut five times since 2001. During 2009, it was paid only on the portion of an individual's estate worth over $3.5m. As a result, over 99% of all estates were unaffected by the estate tax.