High-frequency trading accounts for as much as 43% of value traded on European equity markets, with activity from investment banks making up more than a fifth of that total, according to a new economic report from Europe’s top securities watchdog.

Based on a sample of 100 stocks from nine European Union countries in May 2013, the European Securities and Markets Authorities found that HFT ranges from 24% to 43% of equity value traded, depending on different methodologies. The lower number includes activity from firm's whose primary business is HFT, while the second is based on statistics such as the lifetime of orders, and captures HFT activity from investment banks.