Strategy. MFS (Massachusetts Financial Services Company, the fund's investment adviser) normally invests the funds assets primarily in a broad range of debt instruments issued by U.S. and foreign corporate, government, and other entities, including below investment grade quality debt instruments and debt instruments of issuers located in emerging market countries. MFS focuses on investing the fund's assets in corporate bonds, mortgage-backed securities and other securitized instruments (including commercial mortgage-backed securities, collateralized debt obligations, and/or other asset-backed securities), U.S. Government securities, and debt instruments of issuers located in emerging market countries. MFS allocates the funds assets across these categories with a view toward broad diversification across and within these categories. MFS normally invests up to 35% of the funds assets, at time … Show more… MFS (Massachusetts Financial Services Company, the fund's investment adviser) normally invests the funds assets primarily in a broad range of debt instruments issued by U.S. and foreign corporate, government, and other entities, including below investment grade quality debt instruments and debt instruments of issuers located in emerging market countries. MFS focuses on investing the fund's assets in corporate bonds, mortgage-backed securities and other securitized instruments (including commercial mortgage-backed securities, collateralized debt obligations, and/or other asset-backed securities), U.S. Government securities, and debt instruments of issuers located in emerging market countries. MFS allocates the funds assets across these categories with a view toward broad diversification across and within these categories. MFS normally invests up to 35% of the funds assets, at time of purchase, in below investment grade quality debt instruments. MFS may purchase or sell securities for the fund on a when-issued, delayed delivery, or forward commitment basis where payment and delivery take place at a future settlement date, including mortgage-backed securities purchased or sold in the to be announced (TBA) market. MFS normally invests the fund's assets across different industries, sectors, countries, and regions, but MFS may invest a significant percentage of the funds assets in issuers in a single industry, sector, country, or region. MFS may invest a significant percentage of the funds assets in a single issuer or a small number of issuers. While MFS may use derivatives for any investment purpose, to the extent MFS uses derivatives, 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. Derivatives include futures, forward contracts, options, and swaps. 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 instruments and their issuers. Quantitative screening tools that systematically evaluate instruments may also be considered. In structuring the fund, MFS also considers top-down factors. Show less