Business / Taxes / Qubes: The NASDAQ Stock Market sells shares in a unit investment trust (UIT) that tracks the NASDAQ 100 Stock Index. This market capitalization weighted index includes the largest 100 companies trading on the NASDAQ and is adjusted quarterly to keep it focused on the strongest performers. The name Qubes comes from the UIT's trading symbol: QQQQ. Qubes resemble Standard & Poor's Depositary Receipts (SPDR), which reflect the performance of the Standard & Poor's 500-stock Index (S&P 500) and the DIAMOND (DIA), which tracks the Dow Jones Industrial Average (DJIA). These investments are also decribed as exchange traded funds.