Columbia Threadneedle Investments and Baillie Gifford are weighing up disclosing a historic active share figure in their fund factsheets, following in the footsteps of US equity boutique Polen Capital, which will push ahead with such a move next month.

Active share, a measure of how far a fund's holdings are distinct from the index, is designed as a measure to distinguish truly active managers from closet indexers - managers which charge active-like fees but in truth track the index they're meant to outperform.