The fund invests primarily in a diversified portfolio of Build America Bonds (BABs). Up to 20% may be invested in other securities, including taxable and tax-exempt municipal securities and US Treasury and other government securities. Also, the fund invests at least 80% of its managed assets in securities rated, at the time of investment, investment grade (Baa/BBB or better by S&P, Moody’s, or Fitch) or, if they are unrated, are judged to be of comparable quality by Nuveen Asset Management. The fund uses leverage. As of 1/1/2013, there has been no new issuance of BABs or similarly US Treasury-subsidized taxable municipal bonds for a 24-month period. Because of this, the fund’s contingent term provision is now in force, and the fund will terminate on or around 6/30/2020, distributing the fund’s assets to shareholders at that time.