Even the high-flying exchange stocks were off: NYSE Group fell 5% and the Chicago Mercantile Exchange, now called CME Group, fell 3%.

FORBES: Magazine Article

Harris, who trades for himself and has had stints as a fund manager and as a board member of the Chicago Mercantile Exchange, was part of the group that pushed the Merc to relinquish its mutual structure and become the first exchange to go public, in December 2002.

FORBES: It's Not The Pits

Even as the state deficit persists, other big players such as the CME group, which operates the Chicago Mercantile Exchange, the Chicago Board of Options and Sears are threatening to leave unless their taxes are also lowered.

FORBES: Illinois: State Of Embarrassment

Nasdaq OMX Group competes with other exchanges like NYSE Euronext and Chicago Mercantile Exchange.

FORBES: Higher Algo Trading Volumes Make Nasdaq More Valuable