Table of Contents Duration Short Term Investments 45 The carrying value of the components of the Short term investments are presented in the following table. The investment portfolio is periodically analyzed for changes in duration and related price risk. Additionally, we periodically review the sensitivity of the portfolio to the level of foreign exchange rates and other factors that contribute to market price changes. A summary of these risks and specific analysis on changes is included in the Quantitative and Qualitative Disclosures About Market Risk included under Item 7A. The effective durations of fixed income securities and short term investments are presented in the following table. Amounts presented are net of payable and receivable amounts for securities purchased and sold, but not yet settled. A further consideration in the management of the investment portfolio is the characteristics of the corresponding liabilities and the ability to align the duration of the portfolio to those liabilities and to meet future liquidity needs, minimize interest rate risk and maintain a level of income sufficient to support the underlying insurance liabilities. For portfolios where future liability cash flows are determinable and typically long term in nature, we segregate investments for asset/liability management purposes. The segregated investments support the long term care and structured settlement liabilities in the Life & Group segment. A primary objective in the management of the investment portfolio is to optimize return relative to the corresponding liabilities and respective liquidity needs. Our views on the current interest rate environment, tax regulations, asset class valuations, specific security issuer and broader industry segment conditions as well as domestic and global economic conditions, are some of the factors that enter into an investment decision. We also continually monitor exposure to issuers of securities held and broader industry sector exposures and may from time to time adjust such exposures based on our views of a specific issuer or industry sector. December 31 (In millions) 2018 2017 Short term investments: Commercial paper $ 705 $ 905 U.S. Treasury securities 185 355 Other 396 176 Total short term investments $ 1,286 $ 1,436 December 31 2018 2017 (In millions) Estimated Fair Value Effective Duration (In years) Estimated Fair Value Effective Duration (In years) Investments supporting Life & Group $ 16,212 8.4 $ 16,797 8.4 Other investments 25,428 4.4 26,817 4.4 Total $ 41,640 6.0 $ 43,614 5.9