High-frequency trading (HFT) accounts for 27% of Australian stock market turnover.  Its critics describe it as parasitic and providing toxic liquidity. The Australian Securities and Investment Commission says that most concerns about HFT are unfounded. But controversy is never far from the surface. Last month, the Industry Super Network (ISN) cried foul, claiming high-speed traders could cost Australian investors and retirement savers more than $1.5 billion a year. It prompted Australian School of Business finance professor Mike Aitken to point out that HFT is just the latest in a long list of market innovations and that the ISN should get up to speed, by changing stockbrokers if necessary.