SPDRs (Spiders) are designed to track the value of the Standard & Poor's 500 Composite Price Index. Stands for Standard & Poor's Depositary Receipt. They trade on the American Stock Exchange under the symbol SPY. SPDRs are similar to closed-end funds but are formally known as, a unit investment trust. One SPDR unit is valued at approximately one-tenth (1/10) of the value of the S&P 500. Dividends are disbursed quarterly, and are based on the accumulated stock dividends held in trust, less any expenses of the trust. See: Mid-cap SPDR.