A press release entitled, "Fitch Rates San Diego County Treasurer's Pooled Money Fund 'AAAf/S1' tells us, "Fitch Ratings has assigned 'AAAf/S1' Fund Credit Quality Ratings (FCQR) and Fund Market Risk Sensitivity Ratings to San Diego County Treasurer's Pooled Money Fund, a local government investment pool (LGIP), managed by the San Diego County Treasurer's Office. As of Feb. 2, 2017, the fund has approximately $8.8 billion in invested securities. The ratings reflect Fitch's review of the fund's investment and credit guidelines, the portfolio's credit quality and diversification. The 'AAAf' FCQR indicates the highest underlying credit quality (or lowest vulnerability to default). The 'S1' rating indicates a very low sensitivity to market risk. On a relative basis, changes in net asset value are expected to exhibit high stability, showing low relative volatility across a broad range of market scenarios. The main driver of the fund credit rating is the high credit quality of the portfolio. As per the pool's investment policy, the objectives include the safety and preservation of principal, liquidity sufficient to meet operating cash flow requirements and reasonable rates of return or yield consistent with these objectives." Fitch adds, "As of Feb. 2, 2017, the pool mainly invested in government securities, direct agencies, corporate certificates of deposit and commercial paper. Other permissible securities include securities rated at least 'A/F1' by Fitch or equivalent and medium-term notes, FDIC insured deposit accounts, supranational securities and government money market funds. The pool's weighted average rating factor (WARF) is in line with Fitch's 'AAAf' rating criteria of 0.3 or less. WARF is a risk-weighted measure of a portfolio of assets that accounts for the portfolio's credit quality and maturity profile."