The $40-billion dollar economic hit America took on 9-11 caused a 20% drop in the stock market.  Insurance companies paid claims and we bounced back.  The Stock Market lost about one-third of its value in 2008, partially due to insurance losses.    If you eliminate a large enterprise like health insurance by fiat, the market will crash.  People invested in Hospitals, Drugs, Medical Equipment, and other health related areas, as well as all types of insurance will sell short.   More than 50% of the stock market is owned by individuals, most of that for retirement.  I have friends who had to cancel retirement plans after 9-11.  Foreign investors own 20% of our stock and 40% of bonds because of the stability of our economy.  Seize industries and that money will leave.  This is only the tip of the iceberg of the economic reality of single payer caused turmoil.  Reality says your righteous cause will not fix anthing.  The money needed will not be there in the end.