Yeah and the ratios are already limited by exchanges and the SEC tracks it nicely: http://www.sec.gov/marketstructure/datavis/ma_exchange_canceltotrade.html ht

Yeah and the ratios are already limited by exchanges and the SEC tracks it nicely: http://www.sec.gov/marketstructure/datavis/ma_exchange_canceltotrade.html http://www.sec.gov/marketstructure/datavis/ma_exchange_cance... Some exchanges have a far higher ratio. Instead of ~10 (90%) it's ~150 (99.3%). But there's probably a good reason for this.