Per Nobelist Paul Krugman, a tax on financial transactions could raise “several hundred billion dollars in revenue over the next decade”.
He also notes that Hong Kong and Singapore, “the two countries that score highest on the Heritage Foundation’s Index of Economic Freedom,” already have such taxes.
Also per Krugman: “high-income taxation could shave more than $1 trillion off the deficit.”
That would have a bigger impact on reducing the deficit than any of the major party proposals, including reducing Social Security and Medicare.