If Greek citizens reject austerity measures in Sunday's referendum, there's an 80 percent chance the debt-laden nation will exit the eurozone, according to one strategist. 'I think the market is probably underestimating the chance of a 'no' vote,' Michael Ingram, a market analyst with BGC Partners, told TheStreet TV. 'The vote on Sunday almost doesn't matter because it's essentially between a recession via a 'Grexit' or a depression by signing up for further austerity.' European officials have indicated a reluctance to negotiate with the Greek government should citizens vote 'no' in the July 5 referendum. On Tuesday, Greece missed its $1.8 billion payment to the International Monetary Fund. The country's European bailout program also expired at midnight on Tuesday. Shares of the National Bank of Greece (NBG), which trades in the U.S., rose 7.6% on Wednesday, following hopes of a debt deal. TheStreet's Scott Gamm has details from New York.