Can you shed light but leave everyone in the dark? The Securities and Exchange Commission on Wednesday trumpeted three proposals to increase transparency in “dark pools” – alternative trading systems (ATS) that do not display quotes publicly but account for about 8 per cent of US equity volume.

In announcing possible changes without full details, expected next week, the result was confusion. Those operating pools dedicated to trading large blocks of shares suspected that broker-operated dark pools, which rely heavily on algorithmic trading, would suffer. In fact, the four largest pools, which account for perhaps half of dark pools’ average daily volume, all seem unlikely to face much disruption.