Strategy. MFS (Massachusetts Financial Services Company, the fund's investment adviser) seeks to achieve the funds objective by generating returns from a combination of (1) individual security selection of a combination of debt instruments and equity securities and (2) a tactical asset allocation overlay primarily using derivative instruments to manage the funds exposure to asset classes, markets and currencies. MFS expects to also use derivatives to seek to limit the fund's exposure to certain extreme market events if the fund's exposure to the equity security asset class, after taking into account the tactical overlay, is greater than 35% of the fund's assets. Derivatives include futures, forward contracts, options, and swaps. The fund normally has exposure to at least three different countries and … Show more… MFS (Massachusetts Financial Services Company, the fund's investment adviser) seeks to achieve the funds objective by generating returns from a combination of (1) individual security selection of a combination of debt instruments and equity securities and (2) a tactical asset allocation overlay primarily using derivative instruments to manage the funds exposure to asset classes, markets and currencies. MFS expects to also use derivatives to seek to limit the fund's exposure to certain extreme market events if the fund's exposure to the equity security asset class, after taking into account the tactical overlay, is greater than 35% of the fund's assets. Derivatives include futures, forward contracts, options, and swaps. The fund normally has exposure to at least three different countries and typically has significant long and/or short exposure to foreign securities and foreign currencies. The funds performance may not be correlated with the performance of the asset classes, markets, or currencies represented by the individual investments selected by MFS. Individual Security Selection: In selecting direct investments for the fund, MFS normally invests the funds assets in a combination of debt instruments and equity securities. Debt instruments include corporate bonds, U.S. Government securities, foreign government securities, securitized instruments (including mortgage-backed securities and other asset-backed securities), and other obligations to repay money borrowed. Equity securities include common stocks, depositary receipts, and other securities that represent an ownership interest (or right to acquire an ownership interest) in a company or other issuer. MFS generally invests approximately 65% of the funds assets in debt instruments and cash and/or cash equivalents and approximately 35% of the funds assets in equity securities. These asset class allocations are not designed to take advantage of short-term market opportunities and have been selected for investment over longer time periods. These asset class allocations may be changed without shareholder approval or notice. The actual asset class weightings can deviate due to market movements and cash flows. MFS periodically rebalances the fund's asset class weightings. MFS invests the funds assets in U.S. and foreign securities, including emerging market securities. Of the fund's investments in debt instruments, MFS primarily invests the funds assets in investment grade quality debt instruments, but may also invest the funds assets in below investment grade quality debt instruments. While MFS may invest the equity portion of the funds assets in securities of companies of any size, MFS primarily invests in securities of companies with large capitalizations. Of the fund's investments in equity securities, MFS focuses on investing the fund's assets in the stocks of companies it believes are undervalued compared to their perceived worth (value companies). While MFS may use derivatives for any investment purpose, to the extent MFS uses derivatives as part of its individual security selection process, MFS expects to use derivatives primarily to increase or decrease exposure to a particular market, segment of the market, or security, to increase or decrease interest rate or currency exposure, or as alternatives to direct investments. MFS uses an active bottom-up investment approach to buying and selling investments for the fund. Investments are selected primarily based on fundamental analysis of individual issuers and instruments. Quantitative models that systematically evaluate issuers and instruments are used by certain of the fund's equity securities portfolio managers and may also be considered by the fund's other portfolio managers. Tactical Asset Allocation Overlay : MFS employs a top-down tactical asset allocation process primarily through the use of derivative instruments to adjust the fund's exposure to asset classes, markets, and currencies based on its assessment of the relative attractiveness of such asset classes, markets, and currencies. MFS manages the funds exposure to asset classes, markets and currencies primarily based on its proprietary quantitative models. MFS may also consider current market conditions, its qualitative assessment of the risk/return characteristics of asset classes, markets, and/or currencies, and other factors in structuring the portfolio. In managing the tactical overlay, MFS may increase or decrease the funds exposure to asset classes, markets and/or currencies resulting from MFS individual security selection based on MFS assessment of the risk/return potential of such asset classes, markets and/or currencies. The funds exposure to the equity security asset class, after taking into account the tactical overlay, may generally range from 0% to approximately 70% of the funds assets. Correspondingly, the funds exposure to the debt instrument asset class after taking into account the tactical overlay may at times be as high as 100%. The fund's exposure to non-U.S. dollar currencies after taking into account the tactical overlay may generally range from 0% to approximately 50% of the fund's assets. MFS may also expose the fund to asset classes, markets and/or currencies that are not represented in the individual security selection component of the fund. MFS may adjust the funds net exposure to asset classes, markets and/or currencies by taking net short positions in an asset class, market or currency if MFS believes the risk/return potential of such asset class, market or currency is unattractive. Alternatively, MFS may cause the fund to take net long positions in an asset class, market or currency if MFS believes such asset class, market or currency appears attractive. When MFS' assessment of the relative attractiveness of asset classes and markets is neutral, the fund's exposure to the equity security asset class is expected to be approximately 35% of the fund's assets and the fund's exposure to the debt instrument and cash and/or cash equivalent asset classes is expected to be approximately 65% of the fund's assets. After taking into account the tactical overlay, the fund may have significant exposure to issuers in a single sector, industry, country, or region. MFS' tactical asset allocation process for the fund will typically make extensive use of derivatives. Show less