sentences:  The largest six U.S. banks had assets of $9,576 billion as of year-end 2012, per their 2012 annual reports (SEC Form 10K).For scale, this was 59% of the U.S. GDP for 2012 of $16,245 billion.The top 5 U.S. banks had approximately 30% of the U.S. banking assets in 1998; this rose to 45% by 2008 and to 48% by 2010, before falling to 47% in 2011.