You are assuming that everyone who is having student debt forgiven/paid off by the government has or would have earned the money in question and can now put it into the economy. If that's true then the very reason for absolving the debt, that these people cannot afford to repay their loans, was a lie. More likely they really don't have the money, we're bailing out financial institutions (yet again), and the people who couldn't afford to pay their loans still won't be able to afford to generate enough economic volume to offset this.