Strategy. The Fund is a fund of funds, meaning that it primarily invests its assets in securities of other exchange-traded funds (ETFs). In particular, the Fund allocates its assets among ETFs that each focus on one or more of the following sectors of the fixed income market: (i) securities issued or guaranteed by the U.S. government or its agencies, instrumentalities or sponsored corporations; (ii) inflation protected public obligations of the U.S. Treasury; (iii) U.S. corporate securities; (iv) U.S. mortgage-backed securities; (v) high yield securities (commonly known as junk bonds); (vi) international government and corporate securities, including emerging markets; (vii) first lien senior secured floating rate bank loans; (viii) floating and variable rate securities; and (ix) cash equivalents (i.e., securities maturing in … Show more… The Fund is a fund of funds, meaning that it primarily invests its assets in securities of other exchange-traded funds (ETFs). In particular, the Fund allocates its assets among ETFs that each focus on one or more of the following sectors of the fixed income market: (i) securities issued or guaranteed by the U.S. government or its agencies, instrumentalities or sponsored corporations; (ii) inflation protected public obligations of the U.S. Treasury; (iii) U.S. corporate securities; (iv) U.S. mortgage-backed securities; (v) high yield securities (commonly known as junk bonds); (vi) international government and corporate securities, including emerging markets; (vii) first lien senior secured floating rate bank loans; (viii) floating and variable rate securities; and (ix) cash equivalents (i.e., securities maturing in less than one year) (each, a Fixed Income Sector and collectively, the Fixed Income Sectors). SSGA Funds Management, Inc. (the Adviser or SSGA FM), the Fund's investment adviser, allocates the Fund's assets among the ETFs based on a proprietary sector selection model. The model first incorporates macroeconomic, financial and market data to arrive at a projected return forecast for each Fixed Income Sector. Using these projected return forecasts, the model then allocates the weightings of each Fixed Income Sector to construct a portfolio that seeks to maximize expected total return. The portfolio's final sector allocation is subject to the Adviser's risk and diversification constraints, which limit the amount a Fixed Income Sector may represent in the portfolio and the portfolio's duration relative to the Bloomberg U.S. Aggregate Bond Index. The Adviser may not fully implement the results of the model if it believes the model does not take into account all relevant data, or that a different evaluation or weighting of the data is more appropriate. It is possible the Fund may not have exposure to all Fixed Income Sectors at all times. The Adviser typically rebalances the Fund's portfolio on a monthly basis, although rebalancing may occur more frequently depending on market conditions. The Adviser buys and sells securities for the Fund at each rebalancing based on the results of the process described above. As a result of frequent rebalances, the Fund may experience a high turnover rate. Under normal circumstances, the Fund invests at least 80% of its net assets (plus the amount of borrowings for investments purposes) directly, or indirectly through the underlying ETFs, in fixed income securities. The Fund may invest in ETFs that pay fees to the Adviser and its affiliates for management, marketing or other services. The Fund or ETFs in which the Fund invests may use derivative instruments (primarily options, futures contracts, options on futures, interest rate swaps and credit default swaps) to gain or hedge exposure to certain securities as an alternative to investing directly in such securities. In addition, the Fund may invest in cash and cash equivalents or money market instruments, such as money market funds (including money market funds advised by the Adviser). Show less