Last week, the latest numbers came out on the short interest for stocks, or in other words, the number of shares shorted. One of the industries that was hit hard over the summer, and has generated negative concerns due to the possible connection to the subprime problems, is the investment brokerage field.Many traders have taken extensive short positions in some of these stocks. The brokerage stocks with the greatest short interest, as measured by the short ratio metric, can be found at Stockpickr. The short ratio is also called the "Days to Cover Ratio," which is the number of days the short sellers would need to cover their positions based on the average daily trading volume of shares. The stocks with the higher short ratios, can have greater price spikes when unexpected good news is announced, since the short sellers run to cover their short positions by buying in their shorted shares. For example, earnings above analysts' expectations can cause the stocks to spike from the short-covering. A stock with one of the highest short ratios on the list is Interactive Brokers ( IBKR), with a short ratio of 17. Interactive is an automated global electronic market maker and investment broker, which has a forward price to earnings ratio of 17. The company announced on Sept. 24 that it will now offer trading in Australian stocks and options. Interactive appears in the Barron's: Two Stocks for a Tough Market portfolio at Stockpickr. The other stock in this two-stock portfolio is CME Group ( CME), which has a short ratio of 4. You may know CME as the Chicago Mercantile Exchange.