The great bulk of these interest earnings is sent to the Treasury, thereby helping reduce the government deficit. In the past three years, the Fed remitted $200 billion to the federal government. Ultimately, the securities held by the Fed will mature or will be sold back into the market. So the odds are high that the purchase programs that the Fed has undertaken in support of the recovery will end up reducing, not increasing, the federal debt, both through the interest earnings we send the Treasury and because a stronger economy tends to lead to higher tax revenues and reduced government spending (on unemployment benefits, for example).