Miton UK MicroCap Trust said its net asset value per share rose by 1.82% in the first half, while total returns per share dropped sharply to 1.53p from 11.77p.
The fund underperformed benchmarks, with the FTSE AIM All-Share Total Return Index rising 8.5% and the FTSE SmallCap Total Return Index up 5.0%.
"Both larger and smaller companies find it easier to generate growth when the wider economy is expanding as well," the company said.
"However, one of the overlooked features of microcap stocks is their greater ability to buck the wider economic trend when growth is more subdued."
"The key point is that, during the period of globalisation when growth was plentiful, some microcap advantages were not appreciated. Now that the UK economy is slowing, however, these factors are becoming more important again."