The PowerShares Insured National Municipal Bond Portfolio ETF(Ticker: PZA) seeks investment results that correspond generally to the performance, before fees and expenses, of the Merrill Lynch National Insured Long-Term Core Municipal Securities Index. The index is designed to track the performance and yield of U.S. dollar-denominated investment grade, insured, tax-exempt debt, publicly issued by U.S. municipalities. The Index contains long-term tax-exempt debt and is adjusted monthly. Its constituents are capitalization-weighted based upon their current amount outstanding.